United States General Accounting Office 

GAO	 Report to the Ranking Democratic 

Member, Committee on Transportation 

and Infrastructure, House of 

Representatives 

October 2003 AVIATION SAFETY 

Advancements Being 

Pursued to Improve 

Airliner Cabin 

Occupant Safety and 

Health 

GAO-04-33


a
Highlights of GAO-04-33, a report to the 

Ranking Democratic Member, Committee 

on Transportation and Infrastructure, 

House of Representatives 

Airline travel is one of the safest 

modes of public transportation in 

the United States. Furthermore, 

there are survivors in the majority 

of airliner crashes, according to the 

National Transportation Safety 

Board (NTSB). Additionally, more 

passengers might have survived if 

they had been better protected 

from the impact of the crash, 

smoke, or fire or better able to 

evacuate the airliner. As requested, 

GAO addressed (1) the regulatory 

actions that the Federal Aviation 

Administration (FAA) has taken 

and the technological and 

operational improvements, called 

advancements, that are available or 

are being developed to address 

common safety and health issues in 

large commercial airliner cabins 

and (2) the barriers, if any, that the 

United States faces in 

implementing such advancements. 

This report contains 

recommendations to FAA to 

initiate discussions with NTSB to 

facilitate the exchange of medical 

information from accident 

investigations and to improve the 

cost and effectiveness data 

available for setting priorities for 

research on cabin occupant safety 

and health. FAA generally agreed 

with the report’s contents and its 

recommendations. 

www.gao.gov/cgi-bin/getrpt?GAO-04-33. 

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Gerald 

Dillingham at (202) 512-2834 or 

dillinghamg@gao.gov. 

October 2003 

AVIATION SAFETY 

Advancements Being Pursued to Improve 

Airliner Cabin Occupant Safety and 

Health 

FAA has taken a number of regulatory actions over the past several decades 

to address safety and health issues faced by passengers and flight attendants 

in large commercial airliner cabins. GAO identified 18 completed actions, 

including those that require safer seats, cushions with better fire-blocking 

properties, better floor emergency lighting, and emergency medical kits. 

GAO also identified 28 advancements that show potential to further improve 

cabin safety and health. These advancements vary in their readiness for 

deployment. Fourteen are mature, currently available, and used in some 

airliners. Among these are inflatable lap seat belts, exit doors over the wings 

that swing out on hinges instead of requiring manual removal, and photoluminescent floor lighting. The other 14 advancements are in various stages 

of research, engineering, and development in the United States, Canada, or 

Europe. 

Several factors have slowed the implementation of airliner cabin safety and 

health advancements. For example, when advancements are ready for 

commercial use, factors that may hinder their implementation include the 

time it takes for (1) FAA to complete the rule-making process, (2) U.S. and 

foreign aviation authorities to resolve differences between their respective 

requirements, and (3) the airlines to adopt or install advancements after FAA 

has approved their use. When advancements are not ready for commercial 

use because they require further research, FAA’s processes for setting 

research priorities and selecting research projects may not ensure that the 

limited federal funding for cabin safety and health research is allocated to 

the most critical and cost-effective projects. In particular, FAA does not 

obtain autopsy and survivor information from NTSB after it investigates a 

crash. This information could help FAA identify and target research to the 

primary causes of death and injury. In addition, FAA does not typically 

perform detailed analyses of the costs and effectiveness of potential cabin 

occupant safety and health advancements, which could help it identify and 

target research to the most cost-effective projects. 

A Survivable Large Commercial Airliner Accident 
Contents


Letter


Results in Brief 


Background 


Regulatory Actions Have Been Taken and Additional Advancements 


Are Under Way to Improve Cabin Occupants’ Safety and Health 

Several Factors Have Slowed the Implementation of Cabin 

Occupant Safety and Health Advancements 

Conclusions 

Recommendations for Executive Action 

Agency Comments and Our Evaluation 

1 

3 

7 

9 

19 

28 

29 

30 

Appendixes 

Appendix I: 

Appendix II: 

Appendix III: 

Appendix IV: 

Appendix V: 

Appendix VI: 

Objectives, Scope, and Methodology 31


Canada and Europe Cabin Occupant Safety and Health 


Responsibilities 35


Canada 35


Europe 36


Summary of Key Actions FAA Has Taken to Improve Airliner 


Cabin Safety and Health Since 1984 40


Summaries of Potential Impact Safety Advancements 43 

Retrofitting All Commercial Aircraft with More Advanced Seats 43 

Improving the Ability of Airplane Floors to Hold Seats in an 

Accident 48 

Preventing Overhead Storage Bin Detachment to Protect Passengers 

in an Accident 50 

Child Safety Seats 52 

Inflatable Lap Belt Air Bags 56 

Summaries of Potential Fire Safety Advancements 58 

Fuel Tank Inerting 58 

Arc Fault Circuit Breaker 62 

Multisensor Detectors 64 

Water Mist Fire Suppression 67 

Fire-Safe Fuels 71 

Thermal Acoustic Insulation Materials 73 

Ultra-Fire-Resistant Polymers 76 

Airport Rescue and Fire-Fighting Operations 79 

Summaries of Potential Improved Evacuation Safety 

Advancements 82 

Page i GAO-04-33 Airliner Cabin Occupant Safety and Health 
Contents 

Passenger Safety Briefings 82 

Exit Seat Briefing 84 

Photo-luminescent Floor Track Marking 85 

Crewmember Safety and Evacuation Training 88 

Acoustic Attraction Signals 90 

Smoke Hoods 92 

Exit Slide Testing 97 

Overwing Exit Doors 100 

Next Generation Evacuation Equipment and Procedures 102 

Personal Flotation Devices 104 

Appendix VII:	 Summaries of General Cabin Occupant Safety and Health 

Advancements 106 

Advanced Warnings of Turbulence 106 

Preparations for In-flight Medical Emergencies 107 

Reducing Health Risks to Passengers with Certain Medical 

Conditions 108 

Improved Awareness of Radiation Exposure 110 

Occupational Safety and Health Standards for Flight 

Attendants 112 

Appendix VIII:	 Application of a Cost Analysis Methodology to Inflatable Lap 

Belts 115 

Inflatable Lap Belts 115 

Summary of Results 115 

Methodology 116 

Appendix IX:	 GAO Contacts and Staff Acknowledgments 118 

GAO Contacts 118 

Staff Acknowledgments 118 

Tables	 Table 1: 

Table 2: 

Table 3: 

Table 4: 

Table 5: 

Regulatory Actions Taken by FAA to Improve Cabin


Occupant Safety and Health Since 1984 4


Advancements with Potential to Improve Cabin Occupant 


Safety and Health 4


Status of 10 Significant FAA Rules Pertaining to Airliner 


Cabin Occupants’ Safety and Health, Fiscal Year 1995


through September of Fiscal Year 2003 20


Costs to Equip an Average-sized Airplane in the U.S. Fleet 


with Inflatable Lap Seat Belts, Estimated under Alternative 


Scenarios (In 2002 discounted dollars) 116


Key Assumptions 117


Page ii GAO-04-33 Airliner Cabin Occupant Safety and Health 
Contents 

Figures	 Figure 1: 

Figure 2: 

Figure 3: 

Figure 4: 

Figure 5: 

Figure 6: 

Figure 7: 

Figure 8: 

Figure 9: 

Inflatable Lap Belt Air Bag Inflation Sequence


Manual “Self Help” and “Swing Out” Over-Wing Exits 


Funding for Federal Research on Cabin Occupant Safety 


and Health Issues, by Facility, Fiscal Years 2000-2005


Allocation of Federal Funding for Aircraft Cabin 


Occupant Safety and Health Research, Fiscal Year 


2003


Coach Seating and Impact Position in Coach Seating


Examples of Child Safety Seats


Water Mist Nozzle and Possible Placement


Fire Insulation Blankets


Flammable Cabin Materials and Small-scale Material Test 


Device


11 

15 

25 

26 

45 

53 

68 

74 

77 

80 

83 

87 

90 

94 

98 

102 

Figure 10: Airport Rescue and Fire Training 

Figure 11: Airline Briefing to Passengers on Safety Briefing 

Cards 

Figure 12: Floor Track Marking Using Photo-luminescent 

Materials 

Figure 13: Test Installation of Acoustic Signalling Device 

Figure 14: An Example of a Commercially Available Smoke Hood 

Figure 15: Drawing of Possible Emergency Slide Testing of FAA’s 747 

Test Aircraft 

Figure 16: Airbus’ Planned Double Deck Aircraft 

Page iii GAO-04-33 Airliner Cabin Occupant Safety and Health 
Contents 

Abbreviations 

ACRM Advanced Crew Resource Management


CAMI Civil Aerospace Medical Institute


CRM Crew Resource Management


DGAC Direction Générale de l’Aviation Civile


DOT Department of Transportation


DOT IG Department of Transportation’s Inspector General


DVT deep vein thrombosis


EASA European Aviation Safety Agency


FAA Federal Aviation Administration


ICAO International Civil Aviation Organization 


JAA European Joint Aviation Authorities


NASA National Aeronautics and Space Administration


NIOSH National Institute of Safety and Health


NTSB National Transportation Safety Board


OSHA Occupational Health and Safety Administration


TRL Technical Readiness Level


TSO Technical Standing Order


This is a work of the U.S. government and is not subject to copyright protection in the 

United States. It may be reproduced and distributed in its entirety without further 

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other material, permission from the copyright holder may be necessary if you wish to 

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Page iv GAO-04-33 Airliner Cabin Occupant Safety and Health 
Page 1 GAO-04-33 Airliner Cabin Occupant Safety and Health 

A

United States General Accounting Office 

Washington, D.C. 20548 

October 3, 2003 

The Honorable James L. Oberstar 

Ranking Democratic Member 

Committee on Transportation 

and Infrastructure 

House of Representatives 

Dear Mr. Oberstar: 

Airline travel is one of the safest modes of public transportation in the 

United States, in large part because of the Congress’s, Federal Aviation 

Administration’s (FAA), commercial airlines’, aircraft manufacturers’, and 

airports’ combined efforts to prevent commercial airliner accidents. 

Furthermore, although a few airliner accidents are catastrophic, there are 

survivors in a majority of crashes. According to the National 

Transportation Safety Board (NTSB), passengers survived in 19 of the 26 

U.S. large commercial airliner accidents that occurred from 1982 through 

2001, and in these 19 accidents, over 76 percent of the passengers (1,523 of 

1,988) survived.1

 Additionally, some of the passengers who died in these 

accidents might have survived if they had been better protected from the 

impact of the crash or from the effects of smoke and fire and had been 

better able to evacuate the airliner. This possibility of survival has led 

federal safety officials to focus their efforts not only on preventing airliner 

accidents, but also on increasing the chances of surviving them. 

Over the past several decades, FAA has been taking regulatory actions to 

require the implementation of technological and operational improvements 

in cabin occupant safety and health to help increase passengers’ chances of 

surviving large commercial airliner accidents. In addition, FAA and the 

aviation community have been conducting research on new technological 

and operational improvements, which we refer to in this report as 

advancements, whose implementation could further increase passengers’ 

chances of survival and improve the safety and health of passengers and 

flight attendants. This report discusses regulatory actions that FAA has 

taken as well as potential advancements in cabin occupant safety and 

health that are (1) currently available but not yet implemented or installed, 

and (2) not yet available and subject to additional research to advance the 

1

Large, or ‘transport category’ commercial aircraft are defined as those with a capacity of 30 

or more passengers or a load of 7,500 pounds or more. 

Page 1 GAO-04-33 Airliner Cabin Occupant Safety and Health 
technology or lower costs. For implementation of these advancements to 

occur, FAA often has to take regulatory action, that is, issuing regulations 

or airworthiness directives that require the implementation of 

technological and operational improvements in cabin occupant safety and 

health. FAA continues to pursue regulatory initiatives as well as conduct 

research to improve cabin occupant safety and health. The aviation 

community is also attempting to enhance the safety and health of those 

traveling and working in airliner cabins through such measures as 

providing earlier warnings of turbulence and information on the potential 

to develop blood clots on long-distance flights. Besides increasing cabin 

occupants’ safety and health, these actions and efforts could benefit the 

airlines by helping to restore passengers’ confidence in the safety of flight 

and thereby increasing the demand for air travel, which fell sharply after 

September 11, 2001, and still remains below fiscal year 2000 levels. 

In response to your request, this report addresses the following questions: 

(1) What regulatory actions has FAA taken, and what key advancements 

are available or being developed by FAA and others to address safety and 

health issues faced by passengers and flight attendants in large commercial 

airliner cabins? (2) What factors, if any, slow the implementation of 

advancements in cabin occupant safety and health? In addition, as 

requested, we identified some factors faced by Canada and Europe in their 

efforts to improve cabin occupant safety and health (see app. II). 

To identify the regulatory actions FAA has taken and the key advancements 

that are available or being developed to address safety and health issues 

facing passengers and flight attendants (cabin occupants), we reviewed the 

relevant literature, interviewed FAA officials, and reviewed FAA’s 

documentation on the regulatory actions it has taken to enhance cabin 

occupant safety and health. As part of this effort, FAA officials identified 

key regulatory actions that had been completed in this area. In addition, we 

interviewed other aviation safety experts in government, industry, and 

academia from the United States, Canada, and Europe. (See app. I for 

additional information.) Through our reviews and interviews, we found 

that FAA’s regulatory actions and advancements fell into four broad 

categories—three related to safety in the event of a crash and one related 

to general cabin occupant safety and health. The regulatory actions and 

advancements related to safety in the event of a crash are those actions 

taken to (1) minimize injuries from the impact of a crash, (2) prevent fire or 

mitigate its effects, and (3) improve the chances and speed of evacuation. 

In addition, we discuss the regulatory actions and advancements FAA has 

taken to address a fourth category—improving the safety and health of 

Page 2 GAO-04-33 Airliner Cabin Occupant Safety and Health 
cabin occupants. Using the results of our reviews and interviews, we 

identified and categorized 28 advancements that are currently available or 

being developed, including 5 impact advancements, 8 fire advancements, 

10 evacuation advancements, and 5 cabin occupant safety and health 

advancements. For each of these advancements, we discuss the 

background, research, and regulatory status.2

 We also discuss each 

advancement’s technological readiness for use in the existing commercial 

airliner fleet or in newly produced commercial airplanes. To identify 

factors that have slowed implementation of airliner cabin occupant safety 

and health advancements, we interviewed FAA, NTSB, and industry 

officials. In addition, we analyzed documentation from FAA, NTSB, and 

aviation safety experts to identify factors relating to key issues within FAA 

and the aviation community related to prioritizing and funding research, 

choosing advancements for regulatory implementation, and gaining the 

aviation community’s acceptance of these advancements. 

This report does not address cabin air quality because we are doing work in 

this area for another congressional requester. In addition, given the large 

scope of this review, the report does not focus on safety and health issues 

for flight deck crews (pilots and flight engineers) since they face some 

unique issues not faced by cabin occupants. It also does not address 

aviation security issues, such as hijackings, sabotage, or terrorist activities. 

We conducted our review from January 2002 through September 2003 in 

accordance with generally accepted government auditing standards. 

Results in Brief	 FAA has taken a number of key regulatory actions over the past several 

decades to improve the safety and health of passengers and flight 

attendants in large commercial airliner cabins. We identified 18 such 

completed regulatory actions that FAA has taken since 1984. Table 1 shows 

the number of such actions by category and provides an example for each 

category of action. 

2

In identifying 28 advancements, we are not suggesting that these are the only advancements 

being pursued, rather that these advancements have been recognized by aviation safety 

experts we contacted as offering promise for improving the safety and health of cabin 

occupants. 

Page 3 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Table 1: Regulatory Actions Taken by FAA to Improve Cabin Occupant Safety and 

Health Since 1984 

Number of key 

Category of regulatory action Example actions taken 

Minimize injuries from the impact Stronger seats 

of a crash 

Prevent fire or mitigate its effects Fire-blocking seat cushions 

Improve the chances and speed Emergency floor lighting 

of evacuation 

Improve the safety and health of Onboard emergency medical 

cabin occupants kits 

Source: GAO. 

We also identified 28 advancements that have the potential to increase the 

chances of surviving a commercial airliner crash and to improve the safety 

and health of cabin occupants—both passengers and flight attendants. 

Table 2 shows the number of such advancements by category and provides 

an example for each. 

Table 2: Advancements with Potential to Improve Cabin Occupant Safety and Health 

Number of key 

Category of advancement Example advancements 

Minimize injuries from the impact of Lap seat belts with inflatable air 

a crash bags 

Prevent fire or mitigate its effects Reduced fuel tank flammability 

Improve the chances and speed of Improved passenger safety 

evacuation briefings 

Improve the safety and health of Advanced warnings of 

cabin occupants turbulence 

Source: GAO. 

These 28 advancements vary in their readiness for deployment. For 

example, 14 of the technologies are currently available but not yet 

implemented or installed. Two of these, preparation for in-flight medical 

emergencies and improved insulation, were addressed through separate 

regulations. These regulations require airlines to install additional 

emergency medical equipment (automatic external defibrillators and 

enhanced emergency medical kits) by 2004, replace flammable insulation 

(metalized Mylar®) with improved insulation by 2005, and manufacture 

Page 4 GAO-04-33 Airliner Cabin Occupant Safety and Health 

2 

7 

6 

3 

5 

8 

10 

5 
new large commercial airliners with improved (thermal acoustic) 

insulation beginning September 2, 2005. Another currently available 

advancement is in FAA’s rule-making process—retrofitting the entire 

existing fleet with significantly stronger seats. These seats, commonly 

referred to as 16g seats, for example, can withstand the force of an impact 

16 times a passenger’s body weight (16g), rather than 9 times (9g), as 

currently required primarily for new generation commercial aircraft.3

 For 

the remaining 11 currently available advancements, while FAA does not 

require their use, some are being used by selected airlines. For example, 

some airlines have elected to use inflatable lap seat belts, exit doors over 

the wings that swing out on hinges instead of requiring manual removal, 

and photo-luminescent floor lighting.4

 In addition, some of these 

advancements are available for purchase by the flying public, including 

smoke hoods and child safety seats certified for use on commercial 

airliners. The remaining 14 advancements are in various stages of research, 

engineering, and development in the United States, Canada, or Europe. 

Several factors slow the implementation of advancements in cabin 

occupant safety and health, including those that are currently available, but 

have not yet been implemented or installed and those that require further 

research to demonstrate their effectiveness or lower their costs before they 

are ready for implementation. For those that are ready, and for which 

design and certification standards have been developed, FAA may 

undertake the rule-making process to require their implementation. As our 

prior work has shown, this process can take years. In addition, FAA and its 

international counterparts attempt to reach agreement on, or harmonize, 

their requirements for aviation procedures and equipment. The authorities’ 

current harmonization process has resulted in a backlog, which has slowed 

the implementation of several cabin occupant safety and health 

advancements. Finally, the airlines must implement the advancements. 

While some advancements, such as improved safety briefings, can be 

implemented quickly and economically, others, such as retrofitting 

commercial aircraft with stronger passenger seats, require time3

A separate rule-making effort in 1988 required that newly manufactured aircraft be 

equipped with stronger, 16g seats; however, it did not require that the existing U.S. fleet of 

commercial aircraft be retrofitted with these seats. 

4

FAA officials told us that using photo-luminescent lighting is a different way to meet an 

existing standard and, therefore, should not be considered an advancement in safety. 

However, because photo-luminescent floor lighting differs from standard floor lighting in 

that it works without electricity, some in the aviation community consider it a safety 

advancement. 

Page 5 GAO-04-33 Airliner Cabin Occupant Safety and Health 
consuming, costly changes. FAA may give the airlines several years to 

retrofit their fleets in order to coordinate the change, when possible, with 

existing maintenance schedules and allow the airlines to absorb the 

associated costs. For advancements that require further research before 

they can be considered for use, FAA’s multistep process for identifying 

potential cabin occupant safety and health research projects and allocating 

its limited resources to research projects on the advancements is hampered 

by a lack of autopsy and survivor information and cost and effectiveness 

data. According to FAA researchers, they have not had adequate access to 

autopsy reports and certain survivor information that NTSB obtains from 

autopsy reports and interviews with survivors during its investigations of 

commercial airliner accidents. This information could help FAA to identify 

the principal causes of death and injury and the major factors affecting 

survival, and to target research to advancements addressing these critical 

causes and factors. NTSB told us that while they provide large amounts of 

information on the causes of death and injury in information they make 

publicly available, they would consider making this additional information 

available to FAA if steps were taken to safeguard the privacy of victims and 

survivors. FAA’s multistep process for selecting research projects on 

advancements includes consideration of such factors as their potential 

impact on accident prevention and accident mitigation; however, it does 

not include developing comparable estimates of cost and effectiveness for 

competing advancements to allow direct comparisons between them on 

their potential to reduce injuries and deaths. We developed a cost analysis 

methodology to illustrate how FAA could develop comparable cost 

estimates, to enhance its current process. The results of such analyses 

could be combined with similar estimates of effectiveness using data 

available from a variety of sources, including industry and academia. Using 

comparable cost and effectiveness data across the range of advancements 

could position the agency to choose more effectively between competing 

advancements, taking into account estimates of the number of injuries and 

fatalities that each advancement might prevent for the dollars invested. 

Such cost and effectiveness data would provide a valuable supplement to 

FAA’s current process for setting research priorities and selecting projects 

for funding. 

This report contains a recommendation to the Secretary of Transportation 

to direct the FAA Administrator to initiate discussions with NTSB to 

facilitate the exchange of medical information from accident 

investigations. In addition, the report contains a recommendation to the 

FAA Administrator to improve the analyses available to decision makers 

responsible for setting research priorities and selecting projects for 

Page 6 GAO-04-33 Airliner Cabin Occupant Safety and Health 
improving the safety and health of cabin occupants by (1) developing 

comparable cost estimates of potential advancements competing for 

funding and (2) developing or collecting data on the effectiveness of each 

potential advancement to reduce injuries or fatalities. In commenting on a 

draft of this report, FAA said that they generally agreed with the report’s 

contents and its recommendations. 

Background	 The safe travel of U.S. airline passengers is a joint responsibility of FAA and 

the airlines in accordance with the Federal Aviation Act of 1958, as 

amended, and the Department of Transportation Act, as amended. To carry 

out its responsibilities under these acts, FAA supports research and 

development; certifies that new technologies and procedures are safe; 

undertakes rule-makings, which when finalized form the basis of federal 

aviation regulations; issues other guidance, such as Advisory Circulars; and 

oversees the industry’s compliance with standards that aircraft 

manufacturers and airlines must meet to build and operate commercial 

aircraft. Aircraft manufacturers are responsible for designing aircraft that 

meet FAA’s safety standards, and air carriers are responsible for operating 

and maintaining their aircraft in accordance with the standards for safety 

and maintenance established in FAA’s regulations. FAA, in turn, certifies 

aircraft designs and monitors the industry’s compliance with the 

regulations. 

FAA’s general process for issuing a regulation, or rule, includes several 

steps. When the regulation would require the implementation of a 

technology or operation, FAA first certifies that the technology or 

operation is safe. Then, FAA publishes a notice of proposed rule-making in 

the Federal Register, which sets forth the terms of the rule and establishes 

a period for the public to comment on it. Next, FAA reviews the comments 

by incorporating changes into the rule that it believes are warranted, and, 

in some instances, it repeats these steps one or more times. Finally, FAA 

publishes a final rule in the Federal Register. The final rule includes the 

date when it will go into effect and a time line for compliance. 

Within FAA, the Aircraft Certification Service is responsible for certifying 

that technologies are safe, including improvements to cabin occupant 

safety and health, generally through the issuance of new regulations, a 

finding certifying an equivalent level of safety, or a special condition when 

no rule covers the new technology. The Certification Service is also 

responsible for taking enforcement action to ensure the continued safety of 

aircraft by prescribing standards for aircraft manufacturers governing the 

Page 7 GAO-04-33 Airliner Cabin Occupant Safety and Health 
design, production, and airworthiness of aeronautical products, such as 

cabin interiors. The Flight Standards Service is primarily responsible for 

certifying an airline’s operations (assessing the airline’s ability to carry out 

its operations and maintain the airworthiness of the aircraft) and for 

monitoring the operations and maintenance of the airline’s fleet. 

FAA conducts research on cabin occupant safety and health issues in two 

research facilities, the Mike Monroney Aeronautical Center/Civil 

Aerospace Medical Institute in Oklahoma City, Oklahoma, and the William 

J. Hughes Technical Center in Atlantic City, New Jersey. The institute 

focuses on the impact of flight operations on human health, while the 

technical center focuses on improvements in aircraft design, operation, and 

maintenance and inspection to prevent accidents and improve survivability. 

For the institute or the technical center to conduct research on a project, 

an internal FAA requester must sponsor the project. For example, FAA’s 

Office of Regulation and Certification sponsors much of the two facilities’ 

work in support of FAA’s rule-making activities. FAA also cooperates on 

cabin safety research with the National Aeronautics and Space 

Administration (NASA), academic institutions, and private research 

organizations. 

Until recently, NASA conducted research on airplane crashworthiness at its 

Langley Research Center in Hampton, Virginia. However, because of 

internal budget reallocations and a decision to devote more of its funds to 

aviation security, NASA terminated the Langley Center’s research on the 

crashworthiness of commercial aircraft in 2002. NASA continues to 

conduct fire-related research on cabin safety issues at its Glenn Research 

Center in Cleveland, Ohio. 

NTSB has the authority to investigate civil aviation accidents and collects 

data on the causes of injuries and death for the victims of commercial 

airliner accidents. According to NTSB, the majority of fatalities in 

commercial airliner accidents are attributable to crash impact forces and 

the effects of fire and smoke. Specifically, 306 (66 percent) of the 465 

fatalities in partially survivable U.S. aviation accidents from 1983 through 

2000 died from impact forces, 131 (28 percent) died from fire and smoke, 

and 28 (6 percent) died from other causes.5 

5

NTSB, Survivability of Accidents Involving Part 121 U.S. Air Carrier Operations, 1983 

Through 2000, NTSB/SR-01/01. 

Page 8 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Surviving an airplane crash depends on a number of factors. The space 

surrounding a passenger must remain large enough to prevent the 

passenger from being crushed. The force of impact must also be reduced to 

levels that the passenger can withstand, either by spreading the impact 

over a larger part of the body or by increasing the duration of the impact 

through an energy-absorbing seat or fuselage. The passenger must be 

restrained in a seat to avoid striking the interior of the airplane, and the 

seat must not become detached from the floor. Objects within the airplane, 

such as debris, overhead luggage bins, luggage, and galley equipment, must 

not strike the passenger. A fire in the cabin must be prevented, or, if one 

does start, it must burn slowly enough and produce low enough levels of 

toxic gases to allow the passenger to escape from the airplane. If there is a 

fire, the passenger must not have sustained injuries that prevent him or her 

from escaping quickly. Finally, if the passenger escapes serious injury from 

impact and fire, he or she must have access to exit doors and slides or 

other means of evacuation. 

Regulatory Actions 

Have Been Taken and 

Additional 

Advancements Are 

Under Way to Improve 

Cabin Occupants’ 

Safety and Health 

Over the past several decades, FAA has taken a number of regulatory 

actions designed to improve the safety and health of airline passengers and 

flight attendants by (1) minimizing injuries from the impact of a crash, (2) 

preventing fire or mitigating its effects, (3) improving the chances and 

speed of evacuation, or (4) improving the safety and health of cabin 

occupants. (See app. III for more information on the regulatory actions 

FAA has taken to improve cabin occupant safety and health.) Specifically, 

we identified 18 completed regulatory actions that FAA has taken since 

1984. In addition to these past actions, FAA and others in the aviation 

community are pursuing advancements in these four areas to improve 

cabin occupant safety and health in the future. We identified and reviewed 

28 such advancements—5 to reduce the impact of a crash on occupants, 8 

to prevent or mitigate fire and its effects, 10 to facilitate evacuation from 

aircraft, and 5 to address general cabin occupant safety and health issues. 

Minimizing Injuries from the The primary cause of injury and death for cabin occupants in an airliner 

Impact of a Crash 	 accident is the impact of the crash itself. We identified two key regulatory 

actions that FAA has taken to better protect passengers from impact 

forces. For example, in 1988, FAA required stronger passenger seats for 

newly manufactured commercial airplanes to improve protection in 

Page 9 GAO-04-33 Airliner Cabin Occupant Safety and Health 
survivable crashes.6

 These new seats are capable, for example, of 

withstanding an impact force that is approximately 16 times a passenger’s 

body weight (16g), rather than 9 times (9g), and must be tested dynamically 

(in multiple directions to simulate crash conditions), rather than statically 

(e.g., drop testing to assess the damage from the force of the weight alone 

without motion). In addition, in 1992, FAA issued a requirement for 

corrective action (airworthiness directive) for designs found not to meet 

the existing rules for overhead storage bins on certain Boeing aircraft, to 

improve their crashworthiness after bin failures were observed in the 1989 

crash of an airliner in Kegworth, England, and a 1991 crash near 

Stockholm, Sweden. 

We also identified five key advancements that are being pursued to provide 

cabin occupants with greater impact protection in the future. These 

advancements are either under development or currently available. 

Examples include the following: 

•	 Lap seat belts with inflatable air bags: Lap seat belts that contain 

inflatable air bags have been developed by private companies and are 

currently available to provide passengers with added protection during 

a crash. About 1,000 of these lap seat belts have been installed on 

commercial airplanes, primarily in the seats facing wall dividers 

(bulkheads) to prevent passengers from sustaining head injuries during 

a crash. (See fig. 1.) 

•	 Improved seating systems: Seat safety depends on several interrelated 

systems operating properly, and, therefore, an airline seat is most 

accurately discussed as a system. New seating system designs are being 

developed by manufacturers to incorporate new safety and aesthetic 

designs as well as meet FAA’s 16g seat regulations to better protect 

passengers from impact forces. These seating systems would help to 

ensure that the seats themselves perform as expected (i.e., they stay 

attached to the floor tracks); the space between the seats remains 

adequate in a crash; and the equipment in the seating area, such as 

phones and video screens, does not increase the impact hazard. 

6

FAA subsequently proposed, in October 2002, that the 16g seats be put into the entire 

existing fleet for both passengers and flight attendants within 14 years to better protect 

passengers from impact forces. We included this proposal in our list of advancements. 

Page 10 GAO-04-33 Airliner Cabin Occupant Safety and Health 
•	 Child safety seats: Child safety seats could provide small children with 

additional protection in the event of an airliner crash. NTSB and others 

have recommended their use, and FAA has been involved in this issue 

for at least 15 years. While it has used its rule-making process to 

consider requiring their use, FAA decided not to require child safety 

restraints because its analysis found that if passengers were required to 

pay full fare for children under the age of 2, some parents would choose 

to travel by automobile and, statistically, the chances would increase 

that both the children and the adults would be killed. FAA is continuing 

to consider a child safety seat requirement. 

Figure 1: Inflatable Lap Belt Air Bag Inflation Sequence 

Appendix IV contains additional information on the impact advancements 

we have identified. 

Preventing Fire or 

Mitigating Its Effect 

Fire prevention and mitigation efforts have given passengers additional 

time to evacuate an airliner following a crash or cabin fire. FAA has taken 

seven key regulatory actions to improve fire detection, eliminate potential 

fire hazards, prevent the spread of fires, and better extinguish them. For 

example, to help prevent the spread of fire and give passengers more time 

to escape, FAA upgraded fire safety standards to require that seat cushions 

have fire-blocking layers, which resulted in airlines retrofitting 650,000 

seats over a 3-year period. The agency also set new low heat/smoke 

standards for materials used for large interior surfaces (e.g., sidewalls, 

ceilings, and overhead bins), which FAA officials told us resulted in a 

significant improvement in postcrash fire survivability. FAA also required 

smoke detectors to be placed in lavatories and automatic fire extinguishers 

in lavatory waste receptacles in 1986 and 1987, respectively. In addition, the 

Page 11 GAO-04-33 Airliner Cabin Occupant Safety and Health 
agency required airlines to retrofit their fleets with fire detection and 

suppression systems in cargo compartments, which according to FAA, 

applied to over 3,700 aircraft at a cost to airlines of $300 million. To better 

extinguish fires when they do start, FAA also required, in 1985, that 

commercial airliners carry two Halon fire extinguishers in addition to other 

required extinguishers because of Halon’s superior fire suppression 

capabilities. 

We also identified 8 key advancements that are currently available and 

awaiting implementation or are under development to provide additional 

fire protection for cabin occupants in the future. Examples include the 

following: 

•	 Reduced flammability of insulation materials: To eliminate a potential 

fire hazard, in May 2000, FAA required that air carriers replace 

insulation blankets covered with a type of insulation known as 

metalized Mylar® on specific aircraft by 2005, after it was found that the 

material had ignited and contributed to the crash of Swiss Air Flight 

111.7

 Over 700 aircraft were affected by this requirement. In addition, 

FAA issued a rule in July 2003 requiring that large commercial airplanes 

manufactured after September 2, 2005, be equipped with thermal 

acoustic insulation designed to an upgraded fire test standard that will 

reduce the incidence and intensity of in-flight fires. In addition, after 

September 2, 2007, newly manufactured aircraft must be equipped with 

thermal acoustic materials designed to meet a new standard for burnthrough resistance, providing passengers more time to escape during a 

postcrash fire. 

•	 Reduced fuel tank flammability: Flammable vapors in aircraft fuel 

tanks can ignite. However, currently available technology can greatly 

reduce this hazard by “blanketing” the fuel tank with nonexplosive 

nitrogen-enriched air to suppress (“inert”) the potential for explosion of 

the tank. The U.S. military has used this technology on selected aircraft 

for 20 years, but U.S. commercial airlines have not adopted the 

technology because of its cost and weight. FAA officials told us that the 

military’s technology was also unreliable and designed to meet military 

rather than civilian airplane design requirements. FAA fire safety 

experts have developed a lighter-weight inerting system for center fuel 

tanks, which is simpler than the military system and potentially more 

7

Affected aircraft included Boeing MD-80, MD-88, MD-90, DC-10, and MD-11. 

Page 12 GAO-04-33 Airliner Cabin Occupant Safety and Health 
reliable. Reliability of this technology is a major concern for the aviation 

industry. According to FAA officials, Boeing and Airbus began flight 

testing this technology in July 2003 and August 2003, respectively.

8

 In 

addition, the Air Transport Association (ATA) noted that inerting is only 

one prospective component of an ongoing major program for fuel tank 

safety, and that it has yet to be justified as feasible and cost-effective. 

•	 Sensor technology: Sensors are currently being developed to better 

detect overheated or burning materials. According to FAA and the 

National Institute of Standards and Technology, many current smoke 

and fire detectors are not reliable. For example, a recent FAA study 

reported at least one false alarm per week in cargo compartment fire 

detection systems. The new detectors are being developed by Airbus 

and others in private industry to reduce the number of false alarms. In 

addition, FAA is developing standards that would be used to approve 

new, reduced false alarm sensors. NASA is also developing new sensors 

and detectors. 

•	 Water mist for extinguishing fires: Technology has been under 

development for over two decades to dispense water mist during a fire 

to protect passengers from heat and smoke and prevent the spread of 

fire in the cabin. The most significant development effort has been made 

by a European public-private consortium, FIREDETEX, with over 5 

million euros of European Community funding and a total project cost 

of over 10 million euros (over 10 million U.S. dollars). The development 

of this system was prompted, in part, by the need to replace Halon, 

when it was determined that this main firefighting agent used in fire 

extinguishers aboard commercial airliners depletes ozone in the 

atmosphere. 

Appendix V contains additional information on advancements that address 

fire prevention and mitigation. 

Improving the Chances and Enabling passengers to evacuate more quickly during an emergency has 

Speed of Evacuation	 saved lives. Over the past two decades, FAA has completed regulatory 

action on the following six key requirements to help speed evacuations: 

8

According to FAA, Boeing is flight testing a system similar to the FAA design, and Airbus is 

flight testing the FAA system in an A320. Boeing announced that it would begin installing 

inerting systems similar to the FAA design in their 747s in 2005. 

Page 13 GAO-04-33 Airliner Cabin Occupant Safety and Health 
•	 Improve access to certain emergency exits, such as those generally 

smaller exits above the wing, by providing an unobstructed passageway 

to the exit. 

•	 Install public address systems that are independently powered and can 

be used for at least 10 minutes. 

•	 Help to ensure that passengers in the seats next to emergency exits are 

physically and mentally able to operate the exit doors and assist other 

passengers in emergency evacuations. 

• Limit the distance between emergency exits to 60 feet. 

•	 Install emergency lighting systems that visually identify the emergency 

escape path and each exit. 

• Install fire-resistant emergency evacuation slides. 

We also identified 10 advancements that are either currently available but 

awaiting implementation or require additional research that could lead to 

improved aircraft evacuation, including the following: 

•	 Improved passenger safety briefings: Information is available to the 

airlines on how to develop more appealing safety briefings and safety 

briefing cards so that passengers would be more likely to pay attention 

to the briefings and be better prepared to evacuate successfully during 

an emergency. Research has found that passengers often ignore the oral 

briefings and do not familiarize themselves with the safety briefing 

cards. FAA has requested that air carriers explore different ways to 

present safety information to passengers, but FAA regulates only the 

content of briefings. The presentation style of safety briefings is left up 

to air carriers. 

•	 Over-wing exit doors: Exit doors located over the wings of some 

commercial airliners have been redesigned to “swing out” and away 

from the aircraft so that cabin occupants can exit more easily during an 

emergency. Currently, the over-wing exit doors on most U.S. commercial 

airliners are “self help” doors and must be lifted and stowed by a 

passenger, which can impede evacuation. (See fig. 2.) The redesigned 

doors are now used on new-generation B-737 aircraft operated by one 

U.S. and most European airlines. FAA does not currently require the use 

of over-wing exit doors that swing out because the exit doors that are 

Page 14 GAO-04-33 Airliner Cabin Occupant Safety and Health 
removed manually meet the agency’s safety standards. However, FAA is 

working with the Europeans to develop common requirements for the 

use of this type of exit door. 

•	 Audio attraction signals: The United Kingdom’s Civil Aviation 

Authority and the manufacturer are testing audio attraction signals to 

determine their usefulness to passengers in locating exit doors during 

an evacuation. These signals would be mounted near exits and activated 

during an emergency. The signals would help the passengers find the 

nearest exit even if lighting and exit signs were obscured by smoke. 

Figure 2: Manual “Self Help” and “Swing Out” Over-Wing Exits 

Appendix VI contains additional information on advancements to improve 

aircraft emergency evacuations. 

Improving the Safety and Passengers and flight attendants can face a range of safety and health 

Health of Cabin Occupants 	 effects while aboard commercial airliners. We identified three key actions 

taken by FAA to help maintain the safety and health of passengers and the 

Page 15 GAO-04-33 Airliner Cabin Occupant Safety and Health 
cabin crew during normal flight operations.9

 For example, to prevent 

passengers from being injured during turbulent conditions, FAA initiated 

the Turbulence Happens campaign in 2000 to increase public awareness of 

the importance of wearing seatbelts. The agency has advised the airlines to 

warn passengers to fasten their seatbelts when turbulence is expected, and 

the airlines generally advise or require passengers to keep their seat belts 

fastened while seated to help avoid injuries from unexpected turbulence. 

FAA has also required the airlines to equip their fleets with emergency 

medical kits since 1986. In addition, Congress banned smoking on most 

domestic flights in 1990. 

We also identified five advancements that are either currently available but 

awaiting implementation or require additional research that could lead to 

an improvement in the health of passengers and flight attendants in the 

future. 

•	 Automatic external defibrillators: Automatic external defibrillators are 

currently available for use on some commercial airliners if a passenger 

or crew member requires resuscitation. In 1998, the Congress directed 

FAA to assess the need for the defibrillators on commercial airliners. On 

the basis of its findings, the agency issued a rule requiring that U.S. 

airlines equip their aircraft with automatic external defibrillators by 

2004. According to ATA, most airlines have already done so. 

•	 Enhanced emergency medical kits: In 1998, the Congress directed FAA 

to collect data for 1 year on the types of in-flight medical emergencies 

that occurred to determine if existing medical kits should be upgraded. 

On the basis of the data collected, FAA issued a rule that required the 

contents of existing emergency medical kits to be expanded to deal with 

a broader range of emergencies. U.S. commercial airliners are required 

to carry these enhanced emergency medical kits by 2004. Most U.S. 

airlines have already completed this upgrade, according to ATA. 

•	 Advance warning of turbulence: New airborne weather radar and other 

technologies are currently being developed and evaluated to improve 

the detection of turbulence and increase the time available to cabin 

occupants to avert potential injuries. FAA’s July 2003 draft strategic plan 

established a performance target of reducing injuries to cabin occupants 

caused by turbulence. To achieve this objective, FAA plans to continue 

9

As noted, actions taken to improve cabin air quality will be discussed in another report. 

Page 16 GAO-04-33 Airliner Cabin Occupant Safety and Health 
evaluating new airborne weather radars and other technologies that 

broadly address weather issues, including turbulence. In addition, the 

draft strategic plan set a performance target of reducing serious injuries 

caused by turbulence by 33 percent by fiscal year 2008--using the 

average for fiscal years 2000 through 2002 of 15 injuries per year as the 

baseline and reducing this average to no more than 10 per year. 

•	 Improve awareness of radiation exposure: Flight attendants and 

passengers who fly frequently can be exposed to higher levels of 

radiation on a cumulative basis than the general public. High levels of 

radiation have been linked to an increased risk of cancer and potential 

harm to fetuses. To help passengers and crew members estimate their 

past and future radiation exposure levels, FAA developed a computer 

model, which is publicly available on its Web site 

http://www.jag.cami.jccbi.gov/cariprofile.asp. However, the extent to 

which flight attendants and frequent flyers are aware of cosmic 

radiation’s risks and make use of FAA’s computer model is unclear. 

Agency officials told us that they plan to install a counter capability on 

its Civil Aerospace Medical Institute Web site to track the number of 

visits to its aircrew and passenger health and safety Web site. FAA also 

plans to issue an Advisory Circular by early next year, which 

incorporates the findings of a just completed FAA report, “What 

Aircrews Should Know About Their Occupational Exposure to Ionizing 

Radiation.” This Advisory Circular will include recommended actions 

for aircrews and information on solar flare event notification of 

aircrews. In contrast, airlines in Europe abide by more stringent 

requirements for helping to ensure that cabin and flight crew members 

do not receive excessive doses of radiation from performing their flight 

duties during a given year. For example, in May 1996, the European 

Union issued a directive for workers, including air carrier crew 

members (cabin and flight crews) and the general public, on basic safety 

and health protections against dangers arising from ionizing radiation. 

This directive set dose limits and required air carriers to (1) assess and 

monitor the exposure of all crew members to avoid exceeding exposure 

limits, (2) work with those individuals at risk of high exposure levels to 

adjust their work or flight schedules to reduce those levels, and (3) 

inform crew members of the health risks that their work involves from 

exposure to radiation. It also required airlines to work with female crew 

members, when they announce a pregnancy, to avoid exposing the fetus 

to harmful levels of radiation. This directive was binding for all 

European Union member states and became effective in May 2000. 

Page 17 GAO-04-33 Airliner Cabin Occupant Safety and Health 
•	 Improved awareness of potential health effects related to flying: Air 

travel may exacerbate some medical conditions. Of particular concern is 

a condition known as Deep Vein Thrombosis (DVT), or travelers’ 

thrombosis, in which blood clots can develop in the deep veins of the 

legs from extended periods of inactivity. In a small percentage of cases, 

the clots can break free and travel to the lungs, with potentially fatal 

results. Although steps can be taken to avoid or mitigate some travelrelated health effects, no formal awareness campaigns have been 

initiated by FAA to help ensure that this information reaches physicians 

and the traveling public. The Aerospace Medical Association’s Web site 

http://www.asma.org/publication.html includes guidance for physicians 

to use in advising passengers with preexisting medical conditions on the 

potential risks of flying, as well as information for passengers with such 

conditions to use in assessing their own potential risks. 

See appendix VII for additional information on health-related advances. 

Advancements Vary in Their 

Readiness for Deployment 

The advancements being pursued to improve the safety and health of cabin 

occupants vary in their readiness for deployment. For example, of the 28 

advancements we reviewed, 14 are mature and currently available. Two of 

these, preparation for in-flight medical emergencies and the use of new 

insulation, were addressed through regulations. These regulations require 

airlines to install additional emergency medical equipment (automatic 

external defibrillators and enhanced emergency medical kits) by 2004, 

replace flammable insulation covering (metalized Mylar®) on specific 

aircraft by 2005, and manufacture new large commercial airliners that use a 

new type of insulation meeting more stringent flammability test standards 

after September 2, 2005. Another advancement is currently in the rulemaking process—retrofitting the existing fleet with stronger 16g seats. The 

remaining 11 advancements are available, but are not required by FAA. For 

example, some airlines have elected to use inflatable lap seat belts and exit 

doors over the wings that swing out instead of requiring manual removal, 

and others are using photo-luminescent floor lighting in lieu of or in 

combination with traditional electrical lighting. Some of these 

advancements are commercially available to the flying public, including 

smoke hoods and child safety seats certified for use on commercial 

airliners. The remaining 14 advancements are in various stages of research, 

engineering, and development in the United States, Canada, or Europe. 

Page 18 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Several Factors Have 

Slowed the 

Implementation of 

Cabin Occupant Safety 

and Health 

Advancements 

Several factors have slowed the implementation of airliner cabin occupant 

safety and health advancements in the United States. When advancements 

are available for commercial use but not yet implemented or installed, their 

use may be slowed by the time it takes (1) for FAA to complete the rulemaking process,10 which may be required for an advancement to be 

approved for use but may take many years; (2) for U.S. and foreign aviation 

authorities to resolve differences between their respective cabin occupant 

safety and health requirements; and (3) for the airlines to adopt or install 

advancements after FAA has approved their use, including the time 

required to schedule an advancement’s installation to coincide with major 

maintenance cycles and thereby minimize the costs associated with taking 

an airplane out of service. When advancements are not ready for 

commercial use because they need further research to develop their 

technologies or reduce their costs, their implementation may be slowed by 

FAA’s multistep process for identifying advancements and allocating its 

limited resources to research on potential advancements. FAA’s multistep 

process is hampered by a lack of autopsy and survivor information from 

past accidents and by not having cost and effectiveness data as part of the 

decision process. As a result, FAA may not be identifying and funding the 

most critical or cost-effective research projects. 

FAA’s Rule-making Process 

to Require Advancements 

Can Be Lengthy 

Once an advancement has been developed, FAA may require its use, but 

significant time may be required before the rule-making process is 

complete. One factor that contributes to the length of this process is a 

requirement for cost-benefit analyses to be completed. Time is particularly 

important when safety is at stake or when the pace of technological 

development exceeds the pace of rule-making. As a result, some rules may 

need to be developed quickly to address safety issues or to guide the use of 

new technologies. However, rules must also be carefully considered before 

being finalized because they can have a significant impact on individuals, 

industries, the economy, and the environment. External pressures—such as 

political pressure generated by highly publicized accidents, 

recommendations by NTSB, and congressional mandates—as well as 

internal pressures, such as changes in management’s emphasis, continue to 

add to and shift the agency’s priorities. 

10ATA noted that, for those technologies that are ready, FAA must develop design and 

certification standards before undertaking the rule-making process to require their 

implementation. 

Page 19 GAO-04-33 Airliner Cabin Occupant Safety and Health 
The rule-making process can be long and complicated and has delayed the 

implementation of some technological and operational safety 

improvements, as we reported in July 2001.11 In that report, we reviewed 76 

significant rules in FAA’s workload for fiscal years 1995 through 2000—10 

of the 76 were directly related to improving the safety and health of cabin 

occupants.12 Table 3 details the status or disposition of these 10 rules. The 

shortest rule-making action took 1 year, 11 months (for child restraint 

systems), and the longest took 10 years, 1 month (for the type and number 

of emergency exits). However, one proposed rule was still pending after 15 

years, while three others were terminated or withdrawn after 9 years or 

more. Of the 76 significant rules we reviewed, FAA completed the rulemaking process for 29 of them between fiscal year 1995 and fiscal year 

2000, in a median time of about 2 1⁄2 years to proceed from formal initiation 

of the rule-making process through publication of the final rule; however, 

FAA took 10 years or more to move from formal initiation of the rulemaking process through publication of the final rule for 6 of these 29 rules. 

Table 3: Status of 10 Significant FAA Rules Pertaining to Airliner Cabin Occupants’ Safety and Health, Fiscal Year 1995 through 

September of Fiscal Year 2003 

Rule title Initiation datea Time elapsed Status/disposition 

Flight attendant requirements 2/04/86 9 years, 8 months Terminated/withdrawn 6/06/96 

Type and number of passenger emergency exits 10/15/86 10 years, 1 month Final rule published on 

required in transport category airplanes 11/08/96 

Airworthiness standards; occupant protection 5/29/87 11 years, 1 month Terminated/withdrawn 

standards for commuter category airplanes 6/30/98 

Retrofit of improved seats in air carrier transport 1/26/88 15 years, 6 months Pending 

category airplanes 

Child restraint systems 5/30/90 5 years, 9 months Terminated/withdrawn 

2/13/96 

11U.S. General Accounting Office, Aviation Rule-making: Further Reform Is Needed to 

Address Long-standing Problems, GAO-01-821 (Washington, D.C.: July 9, 2001). 

12Under Executive Order 12866, federal agencies and the Office of Management and Budget 

(OMB) categorize proposed and final rules in terms of their potential impact on the 

economy and the industry affected. The Order defines a regulatory action as “significant” if 

it, among other things, has an annual impact on the economy of $100 million or more and 

adversely affects the economy in a material way. To measure the overall impact of the 1998-

rule-making reforms, through discussions with FAA officials, we created a database of 76 

significant rules. These rules constituted the majority (about 83 percent) of FAA’s significant 

rule workload from fiscal year 1995 through fiscal year 2000. 

Page 20 GAO-04-33 Airliner Cabin Occupant Safety and Health 
(Continued From Previous Page) 

Rule title Initiation datea Time elapsed Status/disposition 

Revised access to Type III exits 10/30/92 9 years, 5 months Withdrawn 

5/03/02 

Child restraint systems 7/18/94 1 year 11 months Final rule published on 6/04/96 

Child restraint systems 4/07/97 6 years, 3 months Pending 

Emergency medical equipment 10/5/98 2 years, 8 months Final rule published on 

6/12/01 

Improved flammability standards for thermal 

acoustic insulation materials in transport category 

aircraft 

12/04/98 4 years, 7 months Final rule published on July 31, 

2003 

Source: GAO analysis of FAA data. 

Note: In commenting on a draft of this report, FAA noted that examining the years elapsed from the 

initiation date of the rule to disposition can be unfair to some actions and that many of the delays were 

not the fault of FAA. 

a

Initiation dates were identified in FAA’s rule-making information system as GAO reported in July 2001. 

This was the only source for data on the agency’s internal milestones, including “initiation date.” 

Differences in U.S. and 

Foreign Requirements Can 

Hamper Adoption of 

Advancements 

FAA and its international counterparts, such as the European Joint Aviation 

Authorities (JAA), impose a number of requirements to improve safety. At 

times, these requirements differ, and efforts are needed to reach agreement 

on procedures and equipment across country borders. In the absence of 

such agreements, the airlines generally must adopt measures to implement 

whichever requirement is more stringent. In 1992, FAA and JAA began 

harmonizing their requirements for (1) the design, manufacture, operation, 

and maintenance of civil aircraft and related product parts; (2) noise and 

emissions from aircraft; and (3) flight crew licensing. Harmonizing the U.S. 

Federal Aviation Regulations with the European Joint Aviation Regulations 

is viewed by FAA as its most comprehensive long-term rule-making effort 

and is considered critical to ensuring common safety standards and 

minimizing the economic burden on the aviation industry that can result 

from redundant inspection, evaluation, and testing requirements. 

According to both FAA and JAA, the process they have used to date to 

harmonize their requirements for commercial aircraft has not effectively 

prioritized their joint recommendations for harmonizing U.S. and European 

aviation requirements, and led to many recommendations going 

unpublished for years. This includes a backlog of over 130 new rule-making 

efforts. The slowness of this process led the United States and Europe to 

develop a new rule-making process to prioritize safety initiatives, focus the 

aviation industry’s and their own limited resources, and establish 

limitations on rule-making capabilities. Accordingly, in March 2003, FAA 

Page 21 GAO-04-33 Airliner Cabin Occupant Safety and Health 
and JAA developed a draft joint “priority” rule-making list; collected and 

considered industry input; and coordinated with FAA’s, JAA’s, and 

Transport Canada Civil Aviation’s management. This effort has resulted in a 

rule-making list of 26 priority projects. In June 2003, at the 20th Annual 

JAA/FAA International Conference, FAA, JAA, and Transport Canada Civil 

Aviation discussed the need to, among other things, support the joint 

priority rule-making list and to establish a cycle for updating it—to keep it 

current and to provide for “pop-up,” or unexpected, rule-making needs. 

FAA and JAA discussed the need to prioritize rule-making efforts to 

efficiently achieve aviation safety goals; that they would work from a 

limited agreed-upon list for future rule-making activities; and that FAA and 

the European Aviation Safety Agency, which is gradually replacing JAA, 

should continue with this approach. 

In the area of cabin occupant safety and heath, some requirements have 

been harmonized, while others have not. For example, in 1996, JAA 

changed its rule on floor lighting to allow reflective, glow-in-the-dark 

material to be used rather than mandating the electrically powered lighting 

that FAA required. The agency subsequently permitted the use of this 

material for floor lighting. In addition, FAA finalized a rule in July 2003 to 

require a new type of insulation designed to delay fire burning though the 

fuselage into the cabin during an accident. JAA favors a performance-based 

standard that would specify a minimum delay in burn-through time, but 

allow the use of different technologies to achieve the standard. FAA 

officials said that the agency would consider other technologies besides 

insulation to achieve burn-through protection but that it would be the 

responsibility of the applicant to demonstrate that the technology provided 

performance equivalent to that stipulated in the insulation rule. JAA 

officials told us that these are examples of the types of issues that must be 

resolved when they work to harmonize their requirements with FAA’s. 

These officials added that this process is typically very time consuming and 

has allowed for harmonizing about five rules per year. 

Page 22 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Significant Time May Be 

Needed to Implement 

Advancements Once They 

Are Required, but Some May 

Enhance Airlines’ 

Competitiveness 

After an advancement has been developed, shown to be beneficial, 

certified, and required by FAA, the airlines or manufacturers need time to 

implement or install the advancement.

13 FAA generally gives the airlines or 

manufacturers a window of time to comply with its rules. For example, 

FAA gave air carriers 5 years to replace metalized Mylar® insulation on 

specific aircraft with a less flammable insulation type, and FAA’s proposed 

rule-making on 16g seats would give the airlines 14 years to install these 

seats in all existing commercial airliners. ATA officials told us that this 

would require replacement of 496,000 seats. 

The airline industry’s recent financial hardships may also delay the 

adoption of advancements. Recently, two major U.S. carriers filed for 

bankruptcy,

14 and events such as the war in Iraq have reduced passenger 

demand and airline revenues below levels already diminished by the events 

of September 11, 2001, and the economic downturn. Current U.S. demand 

for air travel remains below fiscal year 2000 levels. As a result, airlines may 

ask for exemptions from some requirements or extensions of time to install 

advancements. 

While implementing new safety and health advancements can be costly for 

the airlines, making these changes could improve the public’s confidence in 

the overall safety of air travel. In addition, some aviation experts in Europe 

told us that health-related cabin improvements, particularly improvements 

in air quality, are of high interest to Europeans and would likely be used in 

the near future by some European air carriers to set themselves apart from 

their competitors. 

13According to ATA, even if a technology is available in the marketplace, it may not be 

adopted by the airlines until it has been certified by FAA--ensuring that “improvements” do 

not inadvertently compromise overall safety of the aircraft. 

14One of these U.S. carriers is no longer in bankruptcy. 

Page 23 GAO-04-33 Airliner Cabin Occupant Safety and Health 
FAA’s Multistep Process for 

Allocating Limited 

Resources to Research 

Projects Is Hampered by 

Lack of Autopsy and 

Survivor Information and 

Cost and Effectiveness Data 

Federal Research on Aircraft 

Cabin Occupant Safety and 

Health Issues 

For fiscal year 2003, FAA and NASA allocated about $16.2 million to cabin 

occupant safety and health research. FAA’s share of this research 

represented $13.1 million, or about 9 percent of the agency’s Research, 

Engineering, and Development budget of $148 million for fiscal year 2003. 

Given the level of funding allocated to this research effort, it is important to 

ensure that the best research projects are selected. However, FAA’s 

processes for setting research priorities and selecting projects for further 

research are hampered by data limitations. In particular, FAA lacks certain 

autopsy and survivor information from aircraft crashes that could help it 

identify and target research to the most important causes of death and 

injury in an airliner crash. In addition, for the proposed research projects, 

the agency does not (1) develop comparable cost data for potential 

advancements or (2) assess their potential effectiveness in minimizing 

injuries or saving lives. Such cost and effectiveness data would provide a 

valuable supplement to FAA’s current process for setting research priorities 

and selecting projects for funding. 

Both FAA and NASA conduct research on aircraft cabin occupant safety 

and health issues. The Civil Aeromedical Institute (CAMI) and the Hughes 

Technical Center are FAA’s primary facilities for conducting research in this 

area. In addition, two facilities at NASA, the Langley and Glenn research 

centers, have also conducted research in this area. As figure 3 shows, 

federal funding for this research since fiscal year 2000, reached a high in 

fiscal year 2002, at about $17 million, and fell to about $16.2 million in fiscal 

year 2003. The administration’s proposal for fiscal year 2004 calls for a 

further reduction to $15.9 million. This funding covers the expenses of 

researchers at these facilities and of the contracts they may have with 

others to conduct research. In addition, NASA recently decided to end its 

crash research at Langley and to close a drop test facility that it operates in 

Hampton, Virginia. 

Page 24 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Figure 3: Funding for Federal Research on Cabin Occupant Safety and Health 

Issues, by Facility, Fiscal Years 2000-2005 

Note: FAA Hughes Technical Center data includes work in fire-safe fuels, fuel-tank inerting, arc fault 

circuit breakers, and airport rescue and fire-fighting operations. 

In fiscal year 2003, FAA and NASA both supported research projects, 

including aircraft impact, fire, evacuation, and health. As figure 4 shows, 

most of the funding for cabin occupant safety and health research has gone 

to fire-related projects. 

Page 25 GAO-04-33 Airliner Cabin Occupant Safety and Health 
FAA Research Selection Process 

Hampered by Lack of Autopsy 

and Survivor Information and 

Cost and Effectiveness Analyses 

Figure 4: Allocation of Federal Funding for Aircraft Cabin Occupant Safety and 

Health Research, Fiscal Year 2003 

Note: Sum of bars exceeds $16.2 million due to rounding. FAA Technical Center data includes work in 

fire-safe fuels, fuel-tank inerting, arc fault circuit breakers, and airport rescue and fire-fighting 

operations 

To establish research priorities and select projects to fund, FAA uses a 

multistep process. First, within each budget cycle, a number of Technical 

Community Representative Group subcommittees from within FAA 

generate research ideas. Various subcommittees have responsibility for 

identifying potential safety and health projects, including subcommittees 

on crash dynamics, fire safety, structural integrity, passenger evacuation, 

aeromedical, and fuel safety. Each subcommittee proposes research 

projects to review committees, which prioritize the projects. The projects 

are considered and weighted according to the extent to which they address 

(1) accident prevention, (2) accident survival, (3) external requests for 

research, (4) internal requests for research, and (5) technology research 

needs. In addition, the cost of the proposed research is considered before 

arriving at a final list of projects. The prioritized list is then considered by 

the Program Planning Team, which reviews the projects from a policy 

perspective. 

Page 26 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Although the primary causes of death and injury in commercial airliner 

crashes are known to be impact, fire, and impediments to evacuation, FAA 

does not have as detailed an understanding as it would like of the critical 

factors affecting survival in a crash. According to FAA officials, obtaining a 

more detailed understanding of these factors would assist them in setting 

research priorities and in evaluating the relative importance of competing 

research proposals. To obtain a more detailed understanding of the critical 

factors affecting survival, FAA believes that it needs additional information 

from passenger autopsies and from passengers who survived. With this 

information, FAA could then regulate safety more effectively, airplane and 

equipment designers could build safer aircraft, including cabin interiors, 

and more passengers could survive future accidents as equipment became 

safer. 

While FAA has independent authority to investigate commercial airliner 

crashes, NTSB generally controls access to the accident investigation site 

in pursuit of its primary mission of determining the cause of the crash. 

When NTSB concludes its investigation, it returns the airplane to its owner 

and keeps the records of the investigation, including the autopsy reports 

and the information from survivors that NTSB obtains from medical 

authorities and through interviews or questionnaires. NTSB makes 

summary information on the crashes publicly available on its Web site, but 

according to the FAA researchers, this information is not detailed enough 

for their needs. For example, the researchers would like to develop a 

complete autopsy database that would allow them to look for common 

trends in accidents, among other things. In addition, the researchers would 

like to know where survivors sat on the airplane, what routes they took to 

exit, what problems they encountered, and what injuries they sustained. 

This information would help the researchers analyze factors that might 

have an impact on survival. According to the NTSB’s Chief of the Survival 

Factors Division in the Office of Aviation Safety, NTSB provides 

information on the causes of death and a description of injuries in the 

information they make publicly available. In addition, although medical 

records and autopsy reports are not made public, interviews with and 

questionnaires from survivors are available from the public docket. 

NTSB’s Medical Officer was unaware of any formal requests from the FAA 

for the NTSB to provide them with copies of this type of information, 

although the FAA had previously been invited to review such information at 

NTSB headquarters. He added that the Board would likely consider a 

formal request from FAA for copies of autopsy reports and certain survivor 

records, but that it was also likely that the FAA would have to assure NTSB 

Page 27 GAO-04-33 Airliner Cabin Occupant Safety and Health 
that the information would be appropriately safeguarded. According to 

FAA officials, close cooperation between the NTSB and the FAA is needed 

for continued progress in aviation safety. 

Besides lacking detailed information on the causes of death and injury, FAA 

does not develop data on the cost to implement advancements that are 

comparable for each, nor does it assess the potential effectiveness of each 

advancement in reducing injuries and saving lives. Specifically, FAA does 

not conduct cost-benefit analyses as part of its multistep process for setting 

research priorities. Making cost estimates of competing advancements 

would allow direct comparisons across alternatives, which, when 

combined with comparable estimates of effectiveness, would provide 

valuable supplemental information to decision makers when setting 

research priorities. FAA considers its current process to be appropriate and 

sufficient. In commenting on a draft of this report, FAA noted that it is very 

difficult to develop realistic cost data for advancements during the earliest 

stages of research. The agency cautioned that if too much emphasis is 

placed on cost/benefit analyses, potentially valuable research may not be 

undertaken. Recognizing that it is less difficult to develop cost and 

effectiveness information as research progresses, we are recommending 

that FAA develop and use cost and effectiveness analyses to supplement its 

current process. At later stages in the development process, we found that 

this information can be developed fairly easily through cost and 

effectiveness analyses using currently available data. For example, we 

performed an analysis of the cost to implement inflatable lap seat belts 

using a cost analysis methodology we developed (see app. VIII). This 

analysis allowed us to estimate how much this advancement would cost 

per airplane and per passenger trip. Such cost analyses could be combined 

with similar analyses of effectiveness to identify the most cost-effective 

projects, based on their potential to minimize injuries and reduce fatalities. 

Potential sources of effectiveness data include FAA, academia, industry, 

and other aviation authorities. 

Conclusions 	 Although FAA and the aviation community are pursuing a number of 

advancements to enhance commercial airliners’ cabin occupant safety and 

health, several factors have slowed their implementation. For example, for 

advancements that are currently available but are not yet implemented or 

installed, progress is slowed by the length of time it takes for FAA to 

complete its rule-making process, for the U.S and foreign countries to agree 

on the same requirements, and for the airlines to actually install the 

advancements after FAA has required them. In addition, FAA’s multistep 

Page 28 GAO-04-33 Airliner Cabin Occupant Safety and Health 
process for identifying potential cabin occupant safety and health research 

projects and allocating its limited research funding is hampered by the lack 

of autopsy and survivor information from airliner crashes and by the lack 

of cost and effectiveness analysis. Given the level of funding allocated to 

cabin occupant safety and health research, it is important for FAA to 

ensure that this funding is targeting the advancements that address the 

most critical needs and show the most promise for improving the safety 

and health of cabin occupants. However, because FAA lacks detailed 

autopsy and survivor information, it is hampered in its ability to identify the 

principal causes of death and survival in commercial airliner crashes. 

Without an agreement with the National Transportation Safety Board 

(NTSB) to receive detailed autopsy and survivor information, FAA lacks 

information that could be helpful in understanding the factors that 

contribute to surviving a crash. Furthermore, because FAA does not 

develop comparable estimates of cost and effectiveness of competing 

research projects, it cannot ensure that it is funding those technologies 

with the most promise of saving lives and reducing injuries. Such cost and 

effectiveness data would provide a valuable supplement to FAA’s current 

process for setting research priorities and selecting projects for funding. To 

facilitate FAA’s development of comparable cost data across 

advancements, we developed a cost analysis methodology that could be 

combined with a similar analysis of effectiveness to identify the most costeffective projects. Using comparable cost and effectiveness data across the 

range of advancements would position the agency to choose more 

effectively between competing advancements, taking into account 

estimates of the number of injuries and fatalities that each advancement 

might prevent for the dollars invested. In turn, FAA would have more 

assurance that the level of funding allocated to this effort maximizes the 

safety and health of the traveling public and the cabin crew members who 

serve them. 

Recommendations for 

Executive Action 

To provide FAA decision makers with additional data for use in setting 

priorities for research on cabin occupant safety and health and in selecting 

competing research projects for funding, we recommend that the Secretary 

of Transportation direct the FAA Administrator to 

•	 initiate discussions with the National Transportation Safety Board in an 

effort to obtain the autopsy and survivor information needed to more 

fully understand the factors affecting survival in a commercial airliner 

crash and 

Page 29 GAO-04-33 Airliner Cabin Occupant Safety and Health 
•	 supplement its current process by developing and using comparable 

estimates of cost and effectiveness for each cabin occupant safety and 

health advancement under consideration for research funding. 

Agency Comments and 	 We provided copies of a draft of this report to the Department of 

Transportation for its review and comment. FAA generally agreed with the Our Evaluation	 report’s contents and its recommendations. The agency provided us with 

oral comments, primarily technical clarifications, which we have 

incorporated as appropriate. 

As agreed with your office, unless you publicly announce its contents 


earlier, we plan no further distribution of this report until 10 days after the 


date of this letter. At that time, we will send copies to the appropriate 


congressional committees; the Secretary of Transportation; the 


Administrator, FAA; and the Chairman, NTSB. We will also make copies 


available to others upon request. In addition, this report is also available at 


no charge on GAO’s Web site at http://www.gao.gov.


Contacts and staff acknowledgements for this report are included in


appendix IX. If you or your staff have any questions, please contact me or


Glen Trochelman at (202) 512-2834 


Sincerely yours,


Gerald L. Dillingham


Director, Physical Infrastructure Issues


Page 30 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix I 

Objectives, Scope, and Methodology


As requested by the Ranking Democratic Member, House Committee on 

Transportation and Infrastructure, we addressed the following questions: 

(1) What regulatory actions has the Federal Aviation Administration (FAA) 

taken, and what key advancements are available or being developed by 

FAA and others to address safety and health issues faced by passengers and 

flight attendants in large commercial airliner cabins? (2) What factors, if 

any, slow the implementation of advancements in cabin occupant safety 

and health? In addition, as requested, we identified some factors affecting 

efforts by Canada and Europe to improve cabin occupant safety and health. 

The scope of our report includes the cabins of large commercial aircraft 

(those that carry 30 or more passengers) operated by U.S. domestic 

commercial airlines and addresses the safety and health of passengers and 

flight attendants from the time they board the airliner until they disembark 

under normal operational conditions or emergency situations. This report 

identifies cabin occupant safety and health advancements (technological or 

operational improvements) that could be implemented, primarily through 

FAA’s rule-making process. Such improvements include technological 

changes designed to increase the overall safety of commercial aviation as 

well as changes to enhance operational safety. The report does not include 

information on the flight decks of large commercial airliners or safety and 

health issues affecting flight deck crews (pilots and flight engineers), 

because they face some issues not faced by cabin occupants. It also does 

not address general aviation and corporate aircraft or aviation security 

issues, such as hijackings, sabotage, or terrorist activities. 

To identify regulatory actions that FAA has taken to address safety and 

health issues faced by passengers and flight attendants in large commercial 

airliner cabins, we interviewed and collected documentation from U.S. 

federal agency officials on major safety and health efforts completed by 

FAA. The information we obtained included key dates and efforts related to 

cabin occupant safety and health, such as rule-makings, airworthiness 

directives, and Advisory Circulars. 

To identify key advancements that are available or are being developed by 

FAA and others to address safety and health issues faced by passengers and 

flight attendants in large commercial airliner cabins, we consulted experts 

(1) to help ensure that we had included the advancements holding the most 

promise for improving safety and health; and (2) to help us structure an 

evaluation of selected advancements (i.e., confirm that we had included the 

critical benefits and drawbacks of the potential advancements) and 

develop a descriptive analysis for them, where appropriate, including their 

Page 31 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix I


Objectives, Scope, and Methodology


benefits, costs, technology readiness levels, and regulatory status. In 

addition, we interviewed and obtained documentation from federal agency 

officials and other aviation safety experts at the Federal Aviation 

Administration (including its headquarters in Washington, D.C.; Transport 

Airplane Directorate in Renton, Washington; William J. Hughes Technical 

Center in Atlantic City, New Jersey; and Mike Monroney Aeronautical 

Center/Civil Aerospace Medical Institute in Oklahoma City, Oklahoma); 

National Transportation Safety Board; National Aeronautics and Space 

Administration (NASA); Air Transport Association; Regional Airline 

Association; International Air Transport Association; Aerospace Industries 

Association; Aerospace Medical Association; Flight Safety Foundation, 

Association of Flight Attendants; Boeing Commercial Airplane Group; 

Airbus; Cranfield University, United Kingdom; University of Greenwich, 

United Kingdom; National Aerospace Laboratory, Netherlands; Joint 

Aviation Authorities, Netherlands; Civil Aviation, Netherlands; Civil 

Aviation Authority, United Kingdom; RGW Cherry and Associates; Air 

Accidents Investigations Branch, United Kingdom; Syndicat National du 

Personnel Navigant Commercial (French cabin crew union) and ITF Cabin 

Crew Committee, France; BEA (comparable to the U.S. NTSB), France; and 

the Direction Générale de l’Aviation Civile (DGAC), FAA’s French 

counterpart. 

To describe the status of key advancements that are available or under 

development, we used NASA’s technology readiness levels (TRL). These 

levels form a system for ranking the maturity of particular technologies and 

are as follows: 

• TRL 1: Basic principles observed and reported 

• TRL 2: Technology concept and/or application formulated 

•	 TRL 3: Analytical and experimental critical function and/or 

characteristic proof-of-concept developed 

• TRL 4: Component validation in laboratory environment 

• TRL 5: Component and/or validation in relevant environment 

•	 TRL 6: System or subsystem model or prototype demonstrated in a 

relevant environment 

• TRL 7: System prototype demonstrated in a space environment 

Page 32 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix I


Objectives, Scope, and Methodology


•	 TRL 8: Actual system completed and “flight qualified” through test and 

demonstration 

•	 TRL 9: Actual system “flight proven” through successful mission 

operations 

To determine what factors, if any, slow the implementation of 

advancements in cabin occupant safety and health, we reviewed the 

relevant literature and interviewed and analyzed documentation from the 

U.S. federal officials cited above for the 18 key regulatory actions FAA has 

taken since 1984 to improve the safety and health of cabin occupants. We 

used this same approach to assess the regulatory status of the 28 

advancements we reviewed that are either currently available, but not yet 

implemented or installed, or require further research to demonstrate their 

effectiveness or lower their costs. In identifying 28 advancements, GAO is 

not suggesting that these are the only advancements being pursued; rather, 

these advancements have been recognized by aviation safety experts we 

contacted as offering promise for improving the safety and health of cabin 

occupants. To determine how long it generally takes for FAA to issue new 

rules, in addition to speaking with FAA officials, we relied on past GAO 

work and updated it, as necessary. In order to examine the effect of FAA 

and European efforts to harmonize their aviation safety requirements, we 

interviewed and analyzed documentation from aviation safety officials and 

other experts in the United States, Canada, and Europe. Furthermore, to 

examine the factors affecting airlines’ ability to implement or install 

advancements after FAA requires them, we interviewed and analyzed 

documentation from aircraft manufacturers, ATA, and FAA officials. 

In addition, to determine what factors slow implementation we examined 

FAA’s processes for selecting research projects to improve cabin occupant 

safety and health. In examining whether FAA has sufficient data upon 

which to base its research priorities, we interviewed FAA and National 

Transportation Safety Board (NTSB) officials about autopsy and survivor 

information from commercial airliner accidents. We also examined the use 

of cost and effectiveness data in FAA’s research selection process for cabin 

occupant safety and health projects. To facilitate FAA’s development of 

such cost estimates, we developed a cost analysis methodology to illustrate 

how the agency could do this. Specifically, we developed a cost analysis for 

inflatable lap belts to show how data on key cost variables could be 

obtained from a variety of sources. We selected lap belts because they were 

being used in limited situations and appeared to offer some measure of 

improved safety. Information on installation price, annual maintenance and 

Page 33 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix I


Objectives, Scope, and Methodology


refurbishment costs, and added weight of these belts was obtained from 

belt manufacturers. We obtained information from FAA and the 

Department of Transportation’s (DOT) Bureau of Transportation Statistics 

on a number of cost variables, including historical jet fuel prices, the 

impact on jet fuel consumption of carrying additional weight, the average 

number of hours flown per year, the average number of seats per airplane, 

the number of airplanes in the U.S. fleet, and the number of passenger 

tickets issued per year. To account for variation in the values of these cost 

variables, we performed a Monte Carlo simulation.1

 In this simulation, 

values were randomly drawn 10,000 times from probability distributions 

characterizing possible values for the number of seat belts per airplane, 

seat installation price, jet fuel price, number of passenger tickets, number 

of airplanes, and hours flown. This simulation resulted in forecasts of the 

life-cycle cost per airplane, the annualized cost per airplane, and the cost 

per ticket. There is uncertainty in estimating the number of lives potentially 

saved and their value because accidents occur infrequently and 

unpredictably. Such estimates could be higher or lower, depending on the 

number and severity of accidents during a given analysis period and the 

value placed on a human life. 

To identify factors affecting efforts by Canada and Europe to improve cabin 

occupant safety and health we interviewed and collected documentation 

from aviation safety experts in the United States, Canada, and Europe. 

We provided segments of a draft of this report to selected external experts 

to help ensure its accuracy and completeness. These included the Air 

Transport Association, National Transportation Safety Board, Boeing, 

Airbus, and aviation authorities in the United Kingdom, France, Canada 

and the European Union. We incorporated their comments, as appropriate. 

The European Union did not provide comments. 

We conducted our review from January 2002 through September 2003 in 

accordance with generally accepted government auditing standards. 

1

A Monte Carlo simulation is a widely used computational method for generating probability 

distributions of variables that depend on other variables or parameters represented as 

probability distributions. 

Page 34 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix II 

Canada and Europe Cabin Occupant Safety 

and Health Responsibilities 

The United States, Canada, and members of the European Community are 

parties to the International Civil Aviation Organization (ICAO), established 

under the Chicago Convention of 1944, which sets minimum standards and 

recommended practices for civil aviation. In turn, individual nations 

implement aviation standards, including those for aviation safety. While 

ICAO’s standards and practices are intended to keep aircraft, crews, and 

passengers safe, some also address environmental conditions in aircraft 

cabins that could affect the health of passengers and crews. For example, 

ICAO has standards for preventing the spread of disease and for spraying 

aircraft cabins with pesticides to remove disease-carrying insects. 

Canada	 In Canada, FAA’s counterpart for aviation regulations and oversight is 

Transport Canada Civil Aviation, which sets standards and regulations for 

the safe manufacture, operation, and maintenance of aircraft in Canada. In 

addition, Transport Canada Civil Aviation administers, enforces, and 

promotes the Aviation Occupational Health and Safety Program to help 

ensure the safety and health of crewmembers on board aircraft.1

 The 

department also sets the training and licensing standards for aviation 

professionals in Canada, including air traffic controllers, pilots, and aircraft 

maintenance engineers. Transport Canada Civil Aviation has more than 800 

inspectors working with Canadian airline operators, aircraft 

manufacturers, airport operators, and air navigation service providers to 

maintain the safety of Canada’s aviation system. These inspectors monitor, 

inspect, and audit Canadian aviation companies to verify their compliance 

with Transport Canada’s aviation regulations and standards for pilot 

licensing, aircraft certification, and aircraft operation. 

To assess and recommend potential changes to Canada’s aviation 

regulations and standards, the Canadian Aviation Regulation Advisory 

Council was established. This Council is a joint initiative between 

government and the aviation community. The Council supports regulatory 

meetings and technical working groups, which members of the aviation 

community can attend. A number of nongovernmental organizations— 

including airline operators, aviation labor organizations, manufacturers, 

industry associations, and groups representing the public—are members. 

1

The Headquarters Division of Transport Canada provides guidance and assistance to 

Regional Civil Aviation Safety Inspectors – Occupational Health and Safety who conduct 

inspections, investigations, and promotional visits to ensure that airline operators are 

committed to the safety and health of their employees. 

Page 35 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix II


Canada and Europe Cabin Occupant Safety 


and Health Responsibilities


The Transportation Safety Board (TSB) of Canada is similar to NTSB in the 

United States. TSB is a federal agency that operates independently of 

Transport Canada Civil Aviation. Its mandate is to advance safety in the 

areas of marine, pipeline, rail, and aviation transportation by 

•	 conducting independent investigations, including public inquiries when 

necessary, into selected transportation occurrences in order to make 

findings as to their causes and contributing factors; 

•	 identifying safety deficiencies, as evidenced by transportation 

occurrences; 

•	 making recommendations designed to reduce or eliminate any such 

deficiencies; and 

• reporting publicly on their investigations and findings. 

Under its mandate to conduct investigations, TSB conducts safety-issuerelated investigations and studies. It also maintains a mandatory incidentreporting system for all modes of transportation. TSB and Transport 

Canada Civil Aviation use the statistics derived from this information to 

track potential safety concerns in Canada’s transportation system. 

TSB investigates aircraft accidents that occur in Canada or involve aircraft 

built there. Like NTSB, the Transportation Safety Board can recommend air 

safety improvements to Transport Canada Civil Aviation. 

Europe 	 Europe supplements the ICAO framework with the European Civil Aviation 

Conference, an informal forum through which 38 European countries 

formulate policy on civil aviation issues, including safety, but do not 

explicitly address passenger health issues. In addition, the European Union 

issues legislation concerning aviation safety, certification, and licensing 

requirements but has not adopted legislation specifically related to 

passenger health. One European directive requires that all member states 

assess and limit crewmembers’ exposure to radiation from their flight 

duties and provide them with information on the effects of such radiation 

Page 36 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix II


Canada and Europe Cabin Occupant Safety 


and Health Responsibilities


exposure. The European Commission2 is also providing flight 

crewmembers and other mobile workers with free health assessments 

prior to employment, with follow-up health assessments at regular 

intervals. 

Another European supplement to the ICAO framework is the Joint Aviation 

Authorities (JAA), which represents the civil aviation regulatory authorities 

of a number of European states3

 that have agreed to cooperate in 

developing and implementing common safety regulatory standards and 

procedures. JAA uses staff of these authorities to carry out its 

responsibilities for making, standardizing, and harmonizing aviation rules, 

including those for aviation safety, and for consolidating common 

standards among member counties. In addition, JAA is to cooperate with 

other regional organizations or national European state authorities to reach 

at least JAA’s safety level and to foster the worldwide implementation of 

harmonized safety standards and requirements through the conclusion of 

international arrangements. 

Membership in JAA is open to members of the European Civil Aviation 

Conference, which currently consists of 41 member countries. Currently, 37 

countries are members or candidate members of JAA. JAA is funded by 

national contributions; income from the sale of publications and training; 

and income from other sources, such as user charges and European Union 

grants. National contributions are based on indexes related to the size of 

each country’s aviation industry. The “largest” countries (France, Germany, 

and the United Kingdom) each pay around 16 percent and the smallest 

around 0.6 percent of the total contribution income. For 2003, JAA’s total 

budget was about 6.6 million euros. 

In early 1998, JAA launched the Safety Strategy Initiative to develop a 

focused safety agenda to support the “continuous improvement of its 

effective safety system” and further reduce the annual number of accidents 

and fatalities regardless of the growth of air traffic. Two approaches are 

being used to develop the agenda: 

2

The European Union, previously known as the European Community, is an institutional 

framework for the construction of a united Europe. The European Commission is a 

governing body that proposes policies and legislation. 

3

JAA currently has 26 full members and 11 candidate members. 

Page 37 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix II


Canada and Europe Cabin Occupant Safety 


and Health Responsibilities


•	 The “historic approach” is based on analyses of past accidents and has 

led to the identification of seven initial focus areas—controlled flight 

into terrain, approach and landing, loss of control, design related, 

weather, occupant safety and survivability, and runway safety. 

•	 The “predictive approach” or “future hazards approach” is based on an 

identification of changes in the aviation system. 

JAA is cooperating in this effort with FAA and other regulatory bodies to 

develop a worldwide safety agenda and avoid duplication of effort. FAA has 

taken the lead in the historic approach, and JAA has taken the lead in the 

future hazards approach. 

JAA officials told us that they use a consensus-based process to develop 

rules for aviation safety, including cabin occupant safety and health-related 

issues. Reaching consensus among member states is time consuming, but 

the officials said the time invested was worthwhile. Besides making 

aviation-related decisions, JAA identifies and resolves differences in word 

meanings and subtleties across languages—an effort that is critical to 

reaching consensus. JAA does not have regulatory rule-making authority. 

Once the member states are in agreement, each member state’s legislative 

authority must adopt the new requirements. Harmonizing new 

requirements with U.S. and other international aviation authorities further 

adds to the time required to implement new requirements. 

According to JAA officials, they use expert judgment to identify and 

prioritize research and development efforts for aviation safety, including 

airliner cabin occupant safety and health issues, but JAA plans to move 

toward a more data-driven approach.4

 While JAA has no funding of its own 

for research and development, it recommends research priorities to its 

member states. However, JAA officials told us that member states’ research 

and development efforts are often driven by recent airliner accidents in the 

member states, rather than by JAA’s priorities. The planned shift from 

expert judgment to a more data-driven approach will require more 

coordination of aviation research and development across Europe. For 

example, in January 2001, a stakeholder group formed by the European 

Commissioner for Research issued a planning document entitled European 

4

According to officials from the United Kingdom’s Civil Aviation Authority, a JAA member, a 

limited benefit analysis has been developed to provide guidance, but this document has not 

yet been published. 

Page 38 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix II


Canada and Europe Cabin Occupant Safety 


and Health Responsibilities


Aeronautics: A Vision for 2020, which, among other things, characterized 

European aeronautics as a cross-border industry, whose research strategy 

is shaped within national borders, leading to fragmentation rather than 

coherence. The document called for better decision-making and more 

efficient and effective research by the European Union, its member states, 

and aeronautics stakeholders. JAA officials concurred with this 

characterization of European aviation research and development. 

Changes lie ahead for JAA and aviation safety in Europe. The European 

Union recently created a European Aviation Safety Agency, which will 

gradually assume responsibility for rule-making, certification, and 

standardization of the application of rules by the national aviation 

authorities. This organization will eventually absorb all of JAA’s functions 

and activities. The full transition from JAA to the safety agency will take 

several years--per the regulation,5 the European Aviation Safety Agency 

must begin operations by September 28, 2003, and transition to full 

operations by March 2007. 

5

On July 15, 2002, the European Parliament and the Council of the European Union (E.U.) 

adopted Regulation (EC) No 1592/2002 establishing common rules for the E.U. in the field of 

civil aviation and establishing a new European Aviation Safety Agency. 

Page 39 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix III 

Summary of Key Actions FAA Has Taken to 

Improve Airliner Cabin Safety and Health 

Since 1984 

Key improvement areas Action taken Purpose Status 

Impact 

Stronger (16g) passenger FAA required that seats for newly developed To improve the This rule was published on May 

seats aircraft be subjected to more rigorous testing crashworthiness of 17, 1988, and became effective 

than was previously required. The tests subject airplane seats and June 16, 1988. However, only the 

seats to the forward, downward, and other their ability to prevent newest generation of airplanes is 

directional movements that can occur in an or reduce the severity required to have fully tested and 

accident. Likely injuries under various of head, back, and certificated 16g seats. FAA 

conditions are estimated by using instrumented femur injuries. proposed a retrofit rule on October 

crash test dummies. 4, 2002, to phase in 16g seats 

fleetwide within 14 years after 

adoption of the final rule. 

Overhead bins FAA issued an airworthiness directive requiring To improve the The airworthiness directive to 

corrective action for overhead bin designs found crashworthiness of improve bin connectors became 

not to meet the existing rules. some bins after effective November 20, 1992, and 

failures were applied to Boeing 737 and 757 

observed in a 1989 aircraft. 

crash in Kegworth, 

England. 

Fire 

More stringent flammability In 1986, FAA upgraded the fire safety standards To give airliner cabin FAA required that all commercial 

standards for interior for cabin interior materials in transport occupants more time aircraft produced after August 20, 

materials airplanes, establishing a new test method to to evacuate a burning 1988, have panels that exhibit 

determine the heat release from materials 

exposed to radiant heat and set allowable 

criteria for heat release rates. 

airplane by limiting 

heat releases and 

smoke emissions 

when cabin interior 

materials are 

exposed to fire. 

reduced heat releases and smoke 

emissions to delay the onset of 

flashover. Although there was no 

retrofit of the existing fleet, FAA is 

requiring that these improved 

materials be used whenever the 

cabin is substantially refurbished. 

“Fire-blocking” seat In 1984, FAA issued a regulation that enhanced To retard burning of This rule applies to transport 

cushions flammability requirements for seat cushions. cabin materials to category aircraft after November 

increase evacuation 26, 1987. 

time. 

Halon fire extinguishers	 In March 1985, FAA issued a rule requiring at To extinguish in-flight This rule became effective April 

least two Halon fire extinguishers on all fires. 29, 1985, and required 

commercial airliners, in addition to other compliance by April 29, 1986. 

required extinguishers 

Smoke detectors in In March 1985, FAA issued a rule requiring air To identify and This rule became effective on April 

lavatories	 carriers to install smoke detectors in lavatories extinguish in-flight 29, 1985, and required 

within 18 months. fires. compliance by October 29, 1986. 

Fire extinguishers built in to In March 1985, FAA required air carriers to To identify and This rule became effective on April 

lavatory waste receptacles install automatic fire extinguishers in the waste extinguish prevent in- 29, 1985. 

paper bins in all aircraft lavatories. flight fires. This rule required compliance by 

April 29, 1987. 

Page 40 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix III


Summary of Key Actions FAA Has Taken to 


Improve Airliner Cabin Safety and Health 


Since 1984


(Continued From Previous Page) 

Key improvement areas Action taken Purpose Status 

Cargo compartment In 1986, FAA upgraded the airworthiness To improve fire safety This rule required compliance on 

protection standards for ceiling and sidewall liner panels in the cargo and March 20, 1998. 

used in cargo compartments of transport baggage 

category airplanes. compartment of 

certain transport a airplanes. 

Cargo compartment fire In 1998, FAA required air carriers to retrofit the To improve fire safety This rule became effective March 

detection and suppression	 U.S. passenger airliner fleet with fire detection in the cargo and 19, 1998, requiring compliance on 

and suppression systems in certain cargo baggage March 20, 2001. 

compartments. This rule applied to over 3,400 compartment of 

airplanes in service and all newly manufactured certain transport a airplanes. airplanes. 

Evacuation 

Access to exits: Type III This rule requires improved access to the Type To help ensure that This rule became effective June 3, 

exits III emergency exits (typically smaller, overwing 

exits) by providing an unobstructed 

passageway to the exit. Transport aircraft with 

60 or more passenger seats were required to 

comply with the new standards 

passengers have an 

unobstructed 

passageway to exits 

during an 

emergency. 

1992, requiring changes to be 

made by December 3, 1992. 

Public address system: This rule requires that the public address To eliminate reliance This rule became effective 

independent power source	 system be independently powered for at least on engine or November 27, 1989, for air carrier 

10 minutes and that at least 5 minutes of that auxiliary-power-unit and air taxi airplanes 

time is during announcements. operation for manufactured on or after 

emergency November 27, 1990. 

announcements. 

Exit row seating This rule requires that persons seated next to To improve This rule became effective April 5, 

emergency exits be physically and mentally passenger 1990, requiring compliance by 

capable of operating the exit and assisting other evacuation in an October 5, 1990. 

passengers in emergency evacuations. emergency. 

Location of passenger Rule issued to limit the distance between To improve This rule became effective July 24, 

emergency exits adjacent emergency exits on transport passenger 1989, imposing requirements on 

airplanes to 60 feet. evacuation in an airplanes manufactured after 

emergency. October 16, 1987. 

Floor proximity emergency Airplane emergency lighting systems must To improve This rule became effective 

escape path marking visually identify the emergency escape path passenger November 26, 1984, requiring 

and identify each exit from the escape path. 	 evacuation when implementation for large transport 

smoke obscures airplanes by November 26, 1986. 

overhead lighting. 

Fire-resistant evacuation Emergency evacuation slides manufactured To improve This technical standard became 

slides after December 3, 1984, must be fire resistant passenger effective for all evacuation slides 

and comply with new radiant heat testing evacuation. manufactured after December 3, 

procedures. 

b 1984. 

General safety and health 

Preparation for in-flight In 1986, FAA issued a rule requiring To improve air This rule became effective August 

emergencies commercial airlines to carry emergency medical carriers’ preparation 1, 1986, requiring compliance as 

kits. for in-flight of that date. 

emergencies. 

Page 41 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix III


Summary of Key Actions FAA Has Taken to 


Improve Airliner Cabin Safety and Health 


Since 1984


(Continued From Previous Page) 

Key improvement areas Action taken Purpose Status 

Ban on smoking for In 1988 and 1989, the Congress passed To limit the impact of These laws became effective in 

majority of domestic legislation banning smoking on domestic flights poor cabin air quality 1988, and 1990, respectively. 

commercial flights of varying durations. on occupants’ health 

Prevention of in-flight In June 1995, following two serious events To prevent passenger Information is currently posted on 

injuries	 involving turbulence, FAA issued a public injuries from FAA’s Web site. 

advisory to airlines urging the use of seat belts turbulence by 

at all times when passengers are seated but increasing public 

concluded that existing rules did not require awareness of the 

strengthening. importance of 

wearing seatbelts. 

In May 2000, FAA instituted the Turbulence 

Happens public awareness campaign. 

Source: GAO presentation of FAA information. 

a

Technical Class C category cargo compartments are required to have built-in extinguishing systems to 

control fire in lieu of crewmember accessibility. Class D category cargo compartments are required to 

completely contain a fire without endangering the safety of the airplane occupants. 

b

Standard Order (TSO)–C69B (‘‘Emergency Evacuation Slides, Ramps, Ramp/Slides, and 

Slide/Rafts’’) prescribes minimum performance standards for emergency evacuation slides, ramps, 

ramp/slides, and slide/rafts, including standards for resistance to radiant heat sources. 

Page 42 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix IV 

Summaries of Potential Impact Safety 

Advancements 

This appendix presents information on the background and status of 

potential advancements in impact safety that we identified, including the 

following: 

• retrofitting all commercial aircraft with more advanced seats, 

• improving the ability of airplane floors to hold seats in an accident, 

• preventing overhead luggage bins from becoming detached or opening, 

• requiring child safety restraints for children under 40 pounds, and 

• installing lap belts with self-contained inflatable air bags.1 

Retrofitting All 

Commercial Aircraft 

with More Advanced 

Seats 

Background	 In commercial transport airplanes, the ability of a seat to protect a 

passenger from the forces of impact in an accident depends on reducing 

the forces of impact to levels that a person can withstand, either by 

spreading the impact over a larger part of the person’s body or by 

decreasing the duration of the impact through the use of energy-absorbing 

seats, an energy-absorbing fuselage and floors, or restraints such as seat 

belts or inflatable seat belt air bags adapted from automobile technology. In 

a 1996 study by R.G.W Cherry & Associates, enhancing occupant restraint 

was ranked as the second most important of 33 potential ways to improve 

air crash survivability.

2

 Boeing officials noted that the industry generally 

1

Officials with the United Kingdom’s Civil Aviation Authority commented that inflatable 

airbags are but one solution for providing upper torso restraint. These officials cited a 

European Union funded “Going Safe” seat, which through an energy-absorbing device 

enables a lap and diagonal belt system to be fitted to an unmodified seat rail. 

2

R.G.W. Cherry & Associates, Analysis of Structural Factors Influencing the Survivability 

of Occupants in Aeroplane Accidents, Civil Aviation Authority, Paper 96011 (London: 

December 1996). 

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agrees with this view but that FAA and the industry are at odds over the 

means of implementing these changes. 

According to an aviation safety expert, seats and restraints should be 

considered as a system that involves 

• the seats themselves, 

• seat restraints such as seat belts, 

• seat connections to the floor, 

• the spacing between seats, and 

• furnishings in the cabin area that occupants could strike in an accident. 

To protect the occupant, a seat must not only absorb energy well but also 

stay attached to the floor of the aircraft. In other words, the “tie-down” 

chain must remain intact. Although aircraft seat systems are designed to 

withstand about 9 to 16 times the force of gravity, the limits of human 

tolerance to impact substantially exceed the aircraft and seat design limits. 

A number of seat and restraint devices have been shown in testing to 

improve survivability in aviation accidents. Several options are to retrofit 

the entire current fleet with fully tested 16g seats, use rearward-facing 

seats, require three-point auto-style seat belts with shoulder harnesses, and 

install auto-style air bags. 

FAA regulations require seats for newly certified airplane designs to pass 

more extensive tests than were previously required to protect occupants 

from impact forces of up to 16 times the force of normal gravity in the 

forward direction; seat certification standards include specific 

requirements to protect against head, spine, and leg injuries (see fig. 5).3 

FAA first required 16g seats and tests for newly designed, certificated 

3

The 1988 seat dynamic performance standards changed seat standards and testing. The 

new standards expanded seat testing to include potential injuries caused by head strikes on 

the back of seats and on stationary bulkheads, as well as criteria limiting lumbar and femur 

loads. These limits, if exceeded, could cause injuries that could prevent evacuation. Seats 

must be tested for forces in several directions to account for forward, downward, and other 

directional movements such as may occur in an accident. Previous FAA regulations required 

seats to be tested in only one primary direction at 9gs of force. The 16g level was adopted 

rather than a higher standard because the floor tracks of many of the airplanes in use in 1988 

would break away upon an impact of more than 16gs. 

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airplanes in 1988; new versions of existing designs were not required to 

carry 16g seats.

4

 Since 1988, however, in anticipation of a fleetwide retrofit 

rule, manufacturers have increasingly equipped new airplanes with “16gcompatible” seats that have some of the characteristics of fully certified 

16g seats.5

 Certifying a narrow-body airplane type to full 16g seat 

certification standards can cost $250,000.

6,7 

Figure 5: Coach Seating and Impact Position in Coach Seating 

4

The initial proposed rule, Retrofit of Improved Seats in Air Carrier Transport-Category 

Airplanes, 53 Fed. Reg. 17650 (1988) proposed requiring compliance with improved 

crashworthiness standards for all seats of transport-category airplanes used under part 121 

and part 135 and prohibiting the operation of these airplanes unless all seats met the 

crashworthiness performance standards required by Improved Seat Safety Standards, 53 

Fed. Reg. 17640 (1988). 

5

In general, most 16g-compatible seats meet the structural requirements of the 16g seat rule 

but do not need to meet the head injury criteria. 

6

Each aircraft type typically has 8 to 10 different types of seats, each of which must be 

certified; a typical economy class seat costs about $1,800. For marketing reasons, airlines 

usually choose their own distinctive seats, which must be certified for each type of airplane 

they fly. 

7

According to a Boeing Official, one cost estimate compiled by ATA and the Aerospace 

Industries Association in response to NPRM 88-8 presented in December 1988 showed the 

recurring per program cost [was listed] at $440,000. 

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In 1998 FAA estimated that 16g seats would avoid between about 210 to 410 

fatalities and 220 to 240 serious injuries over the 20-year period from 1999 

through 2018. A 2000 study funded by FAA and the British Civil Aviation 

Authority estimated that if 16g seats had been installed in all airplanes that 

crashed from 1984 through 1998, between 23 to 51 fewer U.S. fatalities and 

18 to 54 fewer U.S. serious injuries would have occurred over the period. A 

number of accidents analyzed in that study showed no benefit from 16g 

seats because it was assumed that 16g seats would have detached from the 

floor, offering no additional benefits compared with older seats.8 

Worldwide, the study estimated, about 333 fewer fatalities and 354 fewer 

serious injuries would have occurred during the period had the improved 

seats been installed. Moreover, if fire risks had been reduced, the estimated 

benefits of 16g seats might have increased dramatically, as more occupants 

who were assumed to survive the impact but die in the ensuing fire would 

then have survived both the impact and fire.9 

Status	 Seats that meet the 16g certification requirements are currently available 

and have been required on newly certificated aircraft designs since 1988. 

However, newly manufactured airplanes of older certification, such as 

Boeing 737s, 757s, or 767s, were not required to be equipped with 16g 

certified seats. Recently, FAA has negotiated with manufacturers to install 

full 16g seats on new versions of older designs, such as all newly produced 

737s.10 In October 2002, FAA published a new proposal to create a timetable 

for all airplanes to carry fully certified 16g seats within 14 years.11 The 

comment period for the currently proposed rule ended in March 2003. 

8

R.G.W. Cherry & Associates, Benefit Analysis for Aircraft 16-g Dynamic Seats, 

DOT/FAA/AR-00/13 (Washington, D.C.: April 2000). This study examined 25 large 

commercial airplane accidents that occurred from 1984 and through 1998 and possibly 

involved seat-related fatalities or injuries. 

9

In commenting on the proposed 16g seat retrofit rule, Boeing noted that there were 

fundamental, fatal flaws in both the analysis of benefits and the analysis of costs of 

implementing this rule. 

10Until recently, FAA generally did not require a manufacturer to meet new, higher safety 

standards that are put in place after the date the manufacturer applies for a type certificate 

unless FAA can demonstrate that an unsafe condition exists. FAA’s changed product rule 

requires manufacturers to comply with the latest airworthiness standards when significant 

design changes are proposed for a derivative aircraft that will be certificated under an 

amended or supplemental type certificate. 65 Fed. Reg. 36244 (2002). 

11Improved Seats in Air Carrier Transport Category Airplanes, 67 Fed. Reg. 62294 (2002). 

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Under this proposal, airframe manufacturers would have 4 years to begin 

installing 16g seats in newly manufactured aircraft only, and all airplanes 

would have to be equipped with full 16g seats within 14 years or when 

scheduled for normal seat replacement. FAA estimated that upgrading 

passenger and flight attendant seats to meet full 16g requirements would 

avert approximately 114 fatalities and 133 serious injuries over 20 years 

following the effective date of the rule. This includes 36 deaths that would 

be prevented by improvements to flight attendant seats that would permit 

attendants to survive the impact and to assist more passengers in an 

evacuation. 

FAA estimated the costs to avert 114 fatalities and 133 serious injuries at 

$245 million in present-value terms, or $519 million in overall costs, which, 

according to FAA’s analysis, would approximate the monetary benefits 

from the seats.12 FAA estimated that about 7.5 percent of airplane seats 

would have to be replaced before they would ordinarily be scheduled for 

replacement. FAA’s October 2002 proposal divides seats into three classes 

according to their approximate performance level. Although FAA does not 

know how many seats of each type seat are in service, it estimates that 

about 44 percent of commercial-service aircraft are equipped with full 16g 

seats, 55 percent have 16g-compatible seats, and about 1 percent have 9g 

seats. The 16g-compatible or partial 16g seats span a wide range of 

capabilities; some are nearly identical to full 16g seats but have been 

labeled as 16g-compatible to avoid more costly certification, and other 

partial 16g seats offer only minor improvements over the older generation 

of 9g seats. To determine whether these seats have the same performance 

characteristics as full 16g seats, it may be sufficient, in some cases, to 

review the company’s certification paperwork; in other cases, however, full 

crash testing of actual 16g seats may be necessary to determine the level of 

protection provided. 

FAA is currently considering the comments it received on its October 2002 

proposal. Industry comments raised concerns about general costs, the 

costs of retrofitting flight attendant seats, and the possibility that older 

airplanes designed for 9g seats might require structural changes to 

accommodate full 16g seats. One comment expressed the desire to give 

some credit for and “grandfather” in at least some partial 16g seats. 

12FAA assumed benefits of $3 million for an averted fatality and $0.5 million for an averted 

serious injury. 

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Improving the Ability 

of Airplane Floors to 

Hold Seats in an 

Accident 

Background	 In an accident, a passenger’s chances of survival depend on how well the 

passenger cabin maintains “living space” and the passenger is “tied down” 

within that space. Many experts and reports have noted floor retention— 

the ability of the aircraft cabin floor to remain intact and hold the 

passenger’s seat and restraint system during a crash—as critical to 

increasing the passenger’s chances of survival. Floor design concepts 

developed during the late 1940s and 1950s form the basis for the cabin 

floors found in today’s modern airplanes. 

Accident investigations have documented failures of the floor system in 

crashes.13 New 16g seat requirements were developed in the 1980s. 16g 

seats were intended to be retrofitted on aircraft with traditional 9g floors 

and were designed to maximize the capabilities of existing floor strength. 

While 16g seats might be strong, they could also be inflexible and thus fail if 

the floor deformed in a crash. Under the current 16g requirement, the seats 

must remain attached to a deformed seat track and floor structure 

representative of that used in the airplane.14 To meet these requirements, 

the seat was expected to permanently deform to absorb and limit impact 

forces even if the 16g test conditions were exceeded during a crash. 

A major accident related to floor deformation occurred at Kegworth, 

England, in 1989. A Boeing 737-400 airplane flew into an embankment on 

approach to landing. In total, only 21 of the 52 triple seats—all “16gcompatible” —remained fully attached to the cabin floor; 14 of those that 

remained attached were in the area where the wing passes through the 

13A study of survivable accidents that took place from 1970 through 1978 indicated that floor 

deformation during a crash was a primary cause of seat failure in 60 percent of the 

accidents. (Chandler, et al., DOT/FAA/CT-82-118) 

14In the dynamic 16g seat test with a deformed floor, one floor track must be pitched 10 

degrees (up or down) relative to the other floor track, which must in turn be rolled 10 

degrees. 

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cabin and the area is stronger than other areas to support the wing.15 In this 

section of the airplane, the occupants generally survived, even though they 

were exposed to an estimated peak level of 26gs. The front part of the 

airplane was destroyed, including the floor; most of these seats separated 

from the airplane, killing or seriously injuring the occupants. An FAA 

expert noted that the impact was too severe for the airplane to maintain its 

structural integrity and that 16g seats were not designed for an accident of 

that severity. The British Air Accidents Investigation Branch noted that 

fewer injuries occurred in the accident than would probably have been the 

case with earlier-generation seats. However, the Branch also noted that 

“relatively minor engineering changes could significantly improve the 

resilience and toughness of cabin floors . . . and take fuller advantage of the 

improved passenger seats.” The Branch reported that where failures 

occurred, it was generally the seat track along the floor that failed, and not 

the seat, and that the rear attachments generally remained engaged with 

the floor, “at least partially due to the articulated joint built into the rear 

attachment, an innovation largely stemming from the FAA dynamic test 

requirements.” The Branch concluded that “seats designed to these 

dynamic requirements will certainly increase survivability” but “do not 

necessarily represent an optimum for the long term . . . if matched with 

cabin floors of improved strength and toughness.”

16 

Status	 Several reports have recommended structural improvements to floors. A 

case study of 11 major accidents for which detailed information was 

available found floor issues to be a major cause of injury or fatalities in 4 

accidents and a minor cause in 1 accident. Another study estimated the 

past benefits of 16g seats in U.S. accidents between 1984 and 1998 and 

found no hypothetical benefit from 16g seats in a number of accidents 

because the floor was extensively disrupted during impact.17 In other 

15Some 16g-compatible seats were manufactured to meet 16g dynamic testing standards but 

did not complete FAA’s certification process for floor deformation on representative floors 

and seat tracks and technically met only the 9g seat certification requirements. 

16Report on the accident to Boeing 737-400 G-OBME near Kegworth, Leicestershire, on 8 

January 1989, Aircraft Accident Report 4/90, AAIB, DOT, London, HMSO; 

“Recommendations for Injury Prevention in Transport Aviation Accidents,” prepared for 

NASA, Langley Research Center, by Simula Technologies, Inc., February 2, 2000, TR-99112, 

S97324. 

17 “Benefit Analysis for Aircraft 16-g Dynamic Seats,” Final Report, U.S. Department of 

Transportation (DOT/FAA/AR-00/13) and U.K Civil Aviation Authority (CAA Paper 99003). 

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words, unless the accidents had been less severe or the floor and seat 

tracks had been improved beyond the 9g standard on both new and old jets, 

newer 16g seats would not have offered additional benefits compared with 

the older seats that were actually on the airplane during the accidents 

under study. 

A research program on seat and floor strength was recently conducted by 

the French civil aviation authority, the Direction Générale de l’Aviation 

Civile. Initial findings of the research program on seat-floor attachments 

have not shown dramatic results and showed no rupture or plastic 

deformation of any cabin floor parts during a 16g test. However, French 

officials noted that they plan to perform additional tests with more rigid 

seats. Because many factors are involved it is difficult to identify the 

interrelated issues and interactions between seats and floors. A possible 

area for future research, according to French officials, is to examine 

dynamic floor warping during a crash to improve impact performance. 

FAA officials said they have no plans to change floor strength 

requirements. FAA regulations require floors to meet impact forces likely 

to occur in “emergency landing conditions,” or generally about 9gs of 

longitudinal static force. According to several experts, stronger floors 

could improve the performance of 16g seats. In addition, further 

improvement in seats beyond the 16g standard would likely require 

improved floors. 

Preventing Overhead 

Storage Bin 

Detachment to Protect 

Passengers in an 

Accident 

Background	 In an airplane crash, overhead luggage bins in the cabin sometimes detach 

from their mountings along the ceiling and sidewalls and can fall 

completely or allow pieces of luggage to fall on passengers’ heads (See fig. 

6.). While only a few cases have been reported in which the impact from 

dislodged overhead bins was the direct cause of a crash fatality or injury, a 

study for the British Civil Aviation Authority that attempted to identify the 

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specific characteristics of each fatality in 42 fatal accidents estimated that 

the integrity of overhead bin stowage was the 17th most important of 32 

factors used to predict passenger survivability.

18 Maintaining the integrity 

of bins may also help speed evacuation after a crash. 

Safer bins have been designed since bin problems were observed in a 

Boeing 737 accident in Kegworth, England, in 1989, when nearly all the bins 

failed and fell on passengers. FAA tested bins in response to that accident. 

The Kegworth bins were certified to the current FAA 9g longitudinal static 

loading standards, among others. When FAA subsequently conducted 

longitudinal dynamic loading tests on the types of Boeing bins involved, the 

bins failed. Several FAA experts said that the overhead bins on 737s had a 

design flaw. FAA then issued an airworthiness directive that called for 

modifying all bins on Boeing 737 and 757 aircraft. The connectors for the 

bins were strengthened in accordance with the airworthiness directive, and 

the new bins passed FAA’s tests. 

The British Air Accidents Investigation Branch recommended in 1990 that 

the performance of both bins and latches be tested more rigorously, 

including the performance of bins “when subjected to dynamic crash 

pulses substantially beyond the static load factors currently required.” 

NTSB has made similar recommendations. 

Turbulence reportedly injures at least 15 U.S. cabin occupants a year, and 

possibly over 100. Most of these injuries are to flight attendants who are 

unrestrained. Some injuries are caused by luggage falling from bins that 

open in severe turbulence. Estimates of total U.S. airline injuries from binrelated falling luggage range from 1,200 to 4,500 annually, most of which 

occur during cruising rather than during boarding or disembarking.19 

The study for the British Civil Aviation Authority noted above found that as 

many as 70 percent of impact-related accidents involve overhead bins that 

become detached. However, according to the report, bin detachment does 

not appear to be a major factor in occupants’ survival and data are 

insufficient to support a specific determination about the mechanism of 

18R.G.W. Cherry & Associates, Analysis of Structural Factors Influencing the Survivability 

of Occupants in Aeroplane Accidents, Civil Aviation Authority, Paper 96011 (London: 

December 1996). 

19Flight Safety Foundation, “Increased Amount and Types of Carry-On Baggage Bring New 

Industry Responses,” November-December 1997, Vol. 32, No. 6, p. 6. 

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failure. FAA has conducted several longitudinal and drop tests since the 

Kegworth accident, including drops of airplane fuselage sections with 

overhead storage bins installed. A 1993 dynamic vertical drop test showed 

some varying bin performance problems at about 36gs of downward force. 

An FAA longitudinal test in 1999 tested two types of bins at 6g, at the 9g 

FAA certification requirement, and at the 16g level; in the 16g longitudinal 

test, one of the two bins broke free from its support mountings. 

Status	 In addition to the requirement that they withstand forward (longitudinal) 

loads of slightly more than 9gs, luggage bins must meet other directional 

loading requirements.20 Bin standards are part of the general certification 

requirements for all onboard objects of mass. FAA officials said that 

overhead bins no longer present a problem, appear to function as designed, 

and meet standards. An FAA official told us that problems such as those 

identified at Kegworth have not appeared in later crashes. Another FAA 

official said that while Boeing has had some record of bin problems, the 

problems are occasional and quickly rectified through design changes. 

Boeing officials told us that the evidence that bins currently have latch 

problems is anecdotal. 

Suggestions for making bins safer in an accident include adding features to 

absorb impact forces and keep bins attached and closed during structural 

deformation; using dynamic 16g longitudinal impact testing standards 

similar to those for seats; and storing baggage in alternative compartments 

in the main cabin, elsewhere in the aircraft, or under seats raised for that 

purpose. 

Child Safety Seats


Background	 Using a correctly-designed child safety seat that is strapped in an airplane 

seat offers protection to a child in an accident or turbulence (see fig. 6). By 

contrast, according to many experts, holding a child under two years old on 

an adult’s lap, which is permitted, is unsafe for both the child and for other 

20Bins are required to withstand 9g forward (longitudinal), 3g upward, 6g downward, and 

other load requirements. 

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occupants who could be struck by the child in an accident. Requiring child 

safety seats for infants and small children on airplanes is one of NTSB’s 

“most wanted” transportation safety improvements. The British Air 

Accidents Investigation Branch made similar recommendations, as did a 

1997 White House Commission report on aviation. 

Figure 6: Examples of Child Safety Seats 

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An FAA analysis of survivable accidents from 1978 through 1994 found that 

9 deaths, 4 major injuries, and 8 minor injuries to children occurred. The 

analysis also found that the use of child safety seats would have prevented 

5 deaths, all the major injuries, and 4 to 6 of the minor injuries. Child safety 

advocates have pointed to several survivable accidents in which children 

died—a 1994 Charlotte, North Carolina, crash; a 1990 Cove Neck, New 

York, accident; and a 1987 Denver, Colorado, accident—as evidence of the 

need for regulation. 

A 1992 FAA rule required airlines to allow child restraint systems, but FAA 

has opposed mandatory child safety seats on the basis of studies showing 

that requiring adults to pay for children’s seats would induce more car 

travel, which the study said was more dangerous for children than airplane 

travel. One study published in 1995 by DOT estimated that if families were 

charged full fares for children’s seats, 20 percent would choose other 

modes of transportation, resulting in a net increase of 82 deaths among 

children and adults over 10 years. 

If child safety seats are required, airlines may require adults wishing to use 

child safety seats to purchase an extra seat for the child’s safety seat. FAA 

officials told us that they could not require that the seat next to a parent be 

kept open for a nonpaying child. However, NTSB has testified that the 

scenarios for passengers taking other modes of transportation are flawed 

because FAA assumed that airlines would charge full fares for infants 

currently traveling free. NTSB noted in 1996 that airlines would offer 

various discounts and free seats for infants in order to retain $6 billion in 

revenue that would otherwise be lost to auto travel. Airlines have already 

responded to parents who choose to use child restraint systems with 

scheduling flexibility, and many major airlines offer a 50 percent discount 

off any fare for a child under 2 to travel in an approved child safety seat. 

The 1995 DOT study, however, estimated that even if a child’s seat on an 

airplane were discounted 75 percent, some families would still choose car 

travel and that the choice by those families to drive instead of fly would 

result in a net increase of 17 child and adult deaths over 10 years. 

In FAA tests, some but not all commercially available automobile child 

restraint systems have provided adequate protection in tests simulating 

airplane accidents. Prices range from less than $100 for a child safety seat 

marketed for use in both automobiles and airplanes to as much as $1,300 

for a child safety seat developed specifically for use in airplanes. 

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A drawback to having parents, rather than airlines, provide child safety 

seats for air travel is that some models may be more difficult to fit into 

airplane seat belts, making a proper fit more challenging. While the 

performance of standardized airline-provided seats may be better than that 

of varied FAA-certified auto-airplane seats, one airline said that providing 

seats could present logistical problems for them. However, Virgin Atlantic 

Airlines supplies its own specially developed seats and prohibits parents 

from using their own child seats. Because turbulence can be a more 

frequent danger to unrestrained children than accidents, one expert told us 

that a compromise solution might include allowing some type of alternative 

in-flight restraint. 

Status	 Child safety seats are currently available for use on aircraft. The technical 

issues involved in designing and manufacturing safe seats for children to 

use in both cars and airplanes have largely been solved, according to FAA 

policy officials and FAA researchers. Federal regulations establish 

requirements for child safety seats designed for use in both highway 

vehicles and aircraft by children weighing up to 50 pounds. FAA officials 

explained that regulations requiring child safety seats have been delayed, in 

part, because of public policy concerns that parents would drive rather 

than fly if they were required to buy seats for their children. On February 

18, 1998, FAA asked for comments on an advanced notice of proposed rulemaking to require the use of child safety seats for children under the age of 

2. FAA sponsored a conference in December 1999 to examine child 

restraint systems. At that conference, the FAA Administrator said the 

agency would mandate child safety seats in aircraft and provide children 

with the same level of safety as adults. FAA officials told us that they are 

still considering requiring the use of child safety seats but have not made a 

final decision to do so. If FAA does decide to provide “one level of safety” 

for adults and children, as NTSB advocates, parents may opt to drive to 

their destinations to avoid higher travel costs, thereby statistically 

exposing themselves and their children to more danger. In addition, FAA 

will have to decide whether the parents or airlines will provide the seats. 

If FAA decides to require child safety seats, it will need to harmonize its 

requirements with those of other countries where requirements differ, as 

the regulations on child restraint systems vary. In Canada, as in the United 

States, child safety seats are not mandatory on registered aircraft. In 

Europe, the regulations vary from country to country, but no country 

requires their use. Australia’s policy permits belly belts but discourages 

their use. An Australian official said in 1999 that Australia was waiting for 

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the United States to develop a policy in this area and would probably follow 

that policy. 

Inflatable Lap Belt Air 

Bags 

Background	 Lap belts with inflatable air bags are designed to reduce the injuries or 

death that may result when a passenger’s head strikes the airplane interior. 

These inflatable seat belts adapt advanced automobile air bag technology 

to airplane seats in the form of seat belts with embedded air bags. If a 

passenger loses consciousness because of a head injury in an accident, 

even a minor, nonfatal concussion can cause death if the airplane is 

burning and the passenger cannot evacuate quickly. Slowing the duration 

of the impact with an air bag lessens its lethality. According to a 

manufacturer’s tests using airplane seats on crash sleds, lap belts with air 

bags can likely reduce some impact injuries to survivable levels.21 

FAA does not require seats to be tested in sled tests for head impact 

protection when there would be “no impact” with another seat row or 

bulkhead wall, such as when spacing is increased to 42 inches from the 

more typical 35 inches. While more closely spaced economy class seat 

rows can provide head impact protection through energy-absorbing seat 

backs, seats in no impact positions have tested poorly in head injury 

experiments, resulting in severe head strikes against the occupants’ legs or 

the floor, according to the manufacturer. This no impact exemption from 

FAA’s head injury criteria can include exit rows, business class seats, and 

seats behind bulkhead walls and could permit as many as 30 percent of 

seats in some airplanes to be exempt from the head impact safety criteria 

that row-to-row seats must meet. 

Status	 According to the manufacturer, 13 airlines have installed about 1,000 of the 

devices in commercial airliners, mainly at bulkhead seats; about 200 of 

21One manufacturer’s testing shows that the inflatable lap belts can reduce head injury 

criteria scores from about 2,000 to 200-300 in a 16g impact. A score of 1,000 implies a skull 

fracture, possible loss of consciousness, and a 16 percent risk of life-threatening brain 

injury. 

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these are installed in the U.S. fleet. All of the orders and installations so far 

have been done to meet FAA’s seat safety regulations rather than for 

marketing reasons, according to the manufacturer. 

The airlines would appear to benefit from using the devices in bulkhead 

seats if that would allow them to install additional rows of seats. While the 

amount of additional revenue would depend on the airplane design and 

class of seating, two additional seats may produce more net revenue per 

year than the cost for the devices to be installed throughout an aircraft.22 

Economic constraints are acquisition costs, maintenance costs, and 

increased fuel costs due to weight. The units currently weigh about 3 

pounds per seat, or 2 pounds more than current seat belts. According to the 

manufacturer, the air bag lap belts currently cost $950 to $1,100, including 

maintenance. The manufacturer estimated that if 5 percent of all U.S. seat 

positions were equipped with the devices (about 50,000 seats per year), the 

cost would drop to about $300 to $600 per seat, including installation.23 

Lap belt air bags have been commercially available for only a few years. 

FAA’s Civil Aerospace Medical Institute assisted the developers of the 

devices; manufacturers for both passenger and military use (primarily 

helicopter) are conducting ongoing research. FAA and other regulatory 

bodies have no plans to require their installation, but airlines are allowed to 

use them. The extent to which these devices are installed will depend on 

each airline’s analysis of the cost and benefits. 

22At an annual life-cycle cost of approximately $12,000 to outfit an average airliner with lap 

belt air bags on all seats of the U.S. fleet, assuming an installation cost of $450 per seat 

position not including maintenance and replacement costs. A GAO analysis of the 2002 

Annual Report of Southwest Airlines, which has relatively low passenger revenue per 

available seat mile compared with other airlines, found that each seat produced an annual 

net revenue of about $10,000. See appendix VIII for our analysis of the costs associated with 

lap belts. 

23According to the manufacturer, the installation of the most common design requires 

maintenance of one minute per seat position for a diagnostic test every 1,900 flight hours, 

and the devices must be refurbished about once every 7 years at about a third of the initial 

price. 

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Advancements 

This appendix presents information on the background and status of 

potential advancements in fire safety that we identified, including the 

following: 

• preventing fuel tank explosions with fuel tank inerting; 

• preventing in-flight fires with arc fault circuit breakers; 

• identifying in-flight fires with multisensor fire and smoke detectors; 

•	 suppressing in-flight and postcrash fires by using water mist fire 

suppression systems; 

• mitigating postcrash damage and injury by using less flammable fuels; 

•	 mitigating in-flight and postcrash fires by using fire-resistant thermal 

acoustic insulation; 

•	 mitigating fire-related deaths and injuries by using ultra-fire-resistant 

polymers; and 

•	 mitigating fire deaths and injuries with sufficient airport rescue and fire 

fighting. 

Fuel Tank Inerting


Background	 Fuel tank inerting involves pumping nitrogen-enriched air into an airliner’s 

fuel tanks to reduce the concentration of oxygen to a level that will not 

support combustion. Nitrogen gas makes a fuel tank safer by serving as a 

fire suppressant. The process can be performed with both ground-based 

and onboard systems, and it significantly reduces the flammability of the 

center wing tanks, thereby lowering the likelihood of a fuel tank explosion. 

Following the crash of TWA Flight 800 in 1996, in which 230 people died, 

NTSB determined that the probable cause of the accident was an explosion 

in the center wing fuel tank. The explosion resulted from the ignition of 

flammable fuel vapors in this tank, which is located in the fuselage in the 

space between the wing junctions. NTSB subsequently placed the 

improvement of fuel tank design on its list of “Most Wanted Safety 

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Improvements” and recommended that fuel tank inerting be considered an 

option to eliminate the likelihood of fuel tank explosions. 

FAA issued Special Federal Aviation Regulation 881 to eliminate or 

minimize the likelihood of ignition sources by revisiting the fuel tank’s 

design. Issued in 2001, the regulation consists of a series of FAA regulatory 

actions aimed at preventing the failure of fuel pumps and pump motors, 

fuel gauges, and electrical power wires inside these fuel tanks. In late 2002, 

FAA amended the regulation to allow for an “equivalent level of safety” and 

the use of inerting as part of an alternate means of compliance. 

In a 2001 report, an Aviation Rule-making Advisory Committee tasked with 

evaluating the benefits of inerting the center wing fuel tank estimated these 

benefits in terms of lives saved. After projecting possible in-flight and 

ground fuel tank explosions and postcrash fires from 2005 through 2020, 

the committee estimated that 132 lives might be saved from a ground-based 

system and 253 lives might be saved from an onboard system.2 

Status	 Neither of the two major types of fuel tank inerting—ground-based and 

onboard—is currently available for use on commercial airliners because 

additional development is needed.

3 Both types offer benefits and 

drawbacks. 

•	 A ground-based system sends a small amount of nitrogen into the center 

wing tank before departure. Its benefits include that (1) it requires no 

new technology development for installation, (2) the tank can be inerted 

in 20 minutes, and (3) it carries a lesser weight penalty. Its drawbacks 

include that it is unable to inert for descent, landing, and taxiing to the 

1

ATA noted that more than 80 fuel tank Airworthiness Directives have been adopted since 

the crash of TWA Flight 800 and that a similar number of directives are currently under 

development. 

2

The committee also estimated, on the basis of data on nitrogen exposure from the 

Occupational Safety and Health Administration and the National Institute of Occupational 

Safety and Health, that from 24 to 81 lives could be lost over the same period, depending on 

the degree of oxygen depletion. The report did not specifically indicate whether this 

forecast was for a ground-based, onboard, hybrid, or any other inerting system. 

3

By using more general terminology, this terminology excludes hybrid and liquid nitrogen 

inerting systems, also considered by the Aviation Rule-making Advisory Committees for 

their 1998 and 2001 reports. 

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destination gate, and nitrogen supply systems are needed at each 

terminal gate and remote parking area at every airport. 

•	 An onboard system generates nitrogen by transferring some of the 

engine bleed air – air extracted from the jet engines to supply the cabin 

pressurization system in normal flight—through a module that separates 

air into oxygen and nitrogen and discharges the nitrogen enriched air 

into the fuel tank. Its benefits include that (1) it is self-reliant and (2) it 

significantly reduces an airplane’s vulnerability to lightning, static 

electricity, and incendiary projectiles throughout the flight’s duration.4 

Its drawbacks include that it (1) weighs more, (2) increases the aircraft’s 

operating costs, and (3) may decrease the aircraft’s reliability.

5 

According to FAA, its fire safety experts’ efforts to develop a lighter-weight 

system for center wing tank inerting have significantly increased the 

industry’s involvement. Boeing and Airbus are working on programs to test 

inerting systems in flight. For example, Boeing has recently completed a 

flight test program with a prototype system on a 747. 

None of the U.S. commercial fleet is equipped with either ground-based or 

onboard inerting systems, though onboard systems are in use in U.S. and 

European military aircraft. Companies working in this field are focused on 

developing new inerting technologies or modifying existing ones. A 

European consortium is developing a system that combines onboard center 

wing fuel tank inerting with sensors and a water-mist-plus-nitrogen fire 

suppression system for commercial airplanes. 

In late 2002, FAA researchers successfully ground-tested a prototype 

onboard inerting system using current technology on a Boeing 747SP. New 

research also enabled the agency to ease a design requirement, making the 

inerting technology more cost-effective. This new research showed that 

4

According to an FAA safety expert, FAA is addressing only the center wing tank because of 

its significantly higher flammability exposure and the low risk of an explosion in the wing 

tanks. 

5

A current controversial issue is whether inerting technology will be considered flightcritical hardware—and therefore will be required to function properly for the aircraft to fly. 

If it is deemed flight critical, its reliability may affect the dispatch rate of the aircraft. For 

example, if the technology experiences operational problems, the aircraft may be allowed to 

fly only 25 times a week, even if it is scheduled to fly 30 times a week. This problem reduces 

revenue to the airline and is a greater concern for civilian than for military aviation, because 

there are usually replacements for military aircraft. 

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reducing the oxygen level in the fuel tank to 12 percent—rather than 9 

percent, as was previously thought—is sufficient to prevent fuel tank 

explosions in civilian aircraft.6

 FAA also developed a system that did not 

need the compressors that some had considered necessary. Together, these 

findings allowed for reductions in the size and power demands of the 

system. 

FAA plans to focus further development on the more practical and costeffective onboard fuel tank inerting systems. For example, to further 

improve their cost-effectiveness, the systems could be designed both to 

suppress in-flight cargo fires, thereby allowing them to replace Halon 

extinguishing agents, and to generate oxygen for emergency 

depressurizations, thereby allowing them to replace stored oxygen or 

chemical oxygen generators. 

NASA is also conducting longer-term research on advanced technology 

onboard inert gas-generating systems and onboard oxygen-generating 

systems. Its research is intended (1) to develop the technology to improve 

its efficiency, weight, and reliability and (2) to make the technology 

practical for commercial air transport. NASA will fund the development of 

emerging technologies for ground-based technology demonstration in 

fiscal year 2004. NASA is also considering the extension of civilian 

transport inerting technology to all fuel tanks to help protect airplanes 

against terrorist acts during approaches and departures. 

The cost of the system, its corresponding weight, and its unknown 

reliability are the most significant factors affecting the potential use of 

center wing fuel tank inerting. New cost and weight estimates are 

anticipated in 2003. 

6

FAA fuel tank safety experts conducted tests under high temperatures and found that a 

tank with an oxygen level of 12 percent was inert against internal threats, such as sparks 

and hot surfaces. According to one FAA expert, the system provides a “below 12 percent” 

inert tank under all conditions except for a brief time during descent when local pockets in 

the tank may approach 16 percent oxygen. The expert said that at this time, the tank is 

generally cool enough to be nonflammable even with normal air (21 percent oxygen) in the 

tank. If the tank is cool enough, internal threats will not ignite the fuel air mixture. He said 

the probability of explosions is very low in the wing tanks because they are not heated by 

other airplane systems. 

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•	 In 2001, FAA estimated total costs to equip the worldwide fleet at $9.9 

billion for ground-based, and $20.8 billion for onboard, inerting 

systems.7 

•	 In 2002, FAA officials developed an onboard system for B-747 flighttesting. The estimated cost was $460,000. The officials estimated that 

each system after that would cost about $200,000. The weight of the FAA 

prototype system is 160 pounds.8 A year earlier, NASA estimated the 

weight for a B-777 system with technology in use in military aircraft at 

about 550 pounds.9 

Arc Fault Circuit 

Breaker 

Background	 Arcing faults in wiring may provide an ignition source that can start fires. 

Electrical wiring that is sufficiently damaged might cause arcing or direct 

shorting resulting in smoking, overheating, or ignition of neighboring 

materials. A review of data produced by FAA, the Airline Pilots Association, 

and Boeing showed that electrical systems have been a factor in 

approximately 50 percent of all aircraft occurrences involving smoke or 

fire and that wiring has been implicated in about 10 percent of those 

occurrences. In addition, faulty or malfunctioning wiring has been a factor 

in at least 15 accidents or incidents investigated by NTSB since 1983. 

Properly selecting, routing, clamping, tying, replacing, marking, separating, 

and cleaning around wiring areas and proper maintenance all help mitigate 

the potential for wire system failures, such as arcing, that could lead to 

smoke, fire and loss of function. Chemical degradation, age induced 

cracking, and damage due to maintenance may all create a scenario which 

7

These estimates included the costs for modifying aircraft that are currently in service, in 

production, and being designed, and they assumed a predicted reduction in the accident rate 

of 75 percent. 

8

This system does not have the capability to inert the cargo compartment, bay, and wheel 

well, and it dumps oxygen as effluent rather than using it for an emergency passenger 

oxygen system. 

9

A 2001 NASA study indicated that two liquid nitrogen systems were the only ones that 

appeared capable of inerting all fuel tanks of a commercial aircraft full time. 

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could lead to arcing. Arcing can occur between a wire and structure or 

between different wire types. Wire chafing is a sign of degradation; chafing 

happens when the insulation around one wire rubs against a component 

tougher than itself (such as structure or control cable) exposing the wire 

conductor. This condition can lead to arcing. When arcing wires are too 

close to flammable materials or are flammable themselves, fires can occur. 

In general, wiring and wiring insulation degrade for a variety of reasons, 

including age, inadequate maintenance, chemical contamination, improper 

installation or repair, and mechanical damage. Vibration, moisture, and 

heat can contribute to and accelerate degradation. Consequences of wire 

systems failures include loss of function, smoke, and fire. Since most 

wiring is bundled and located in hidden or inaccessible areas, it is difficult 

to monitor the health of an aircraft’s wiring system during scheduled 

maintenance using existing equipment and procedures. Failure 

occurrences have been documented in wiring running to the fuel tank, in 

the electronics equipment compartment, in the cockpit, in the ceiling of the 

cabin, and in other locations. 

To address the concerns with arcing, arc fault circuit breakers for aircraft 

use are being developed. The arc fault circuit breaker cuts power off as it 

senses a wire beginning to arc. It is intended to prevent significant damage 

before a failure develops into a full-blown arc, which can produce 

extremely localized heat, char insulation, and generally create problems in 

the wire bundles. Arc fault circuit protection devices would mitigate arcing 

events, but will not identify the wire breaches and degradation that 

typically lead up to these events. 

Status	 FAA, the Navy, and the Air Force are jointly developing arc fault circuit 

breaker technology. Boeing is also developing a monitoring system to 

detect the status of and changes in wiring; and power shuts down when 

arcing is detected. This system may be able to protect wiring against both 

electrical overheating and arcing and is considered more advanced than the 

government’s circuit breaker technology. 

FAA developed a plan called the Enhanced Airworthiness Program for 

Airplane Systems to address wiring problems, which includes development 

of arc fault circuit breaker technology and installation guidance along with 

proposals of new regulations. The plan provides means for enhancing 

safety in the areas of wire system design, certification, maintenance, 

research and development, reporting, and information sharing and 

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outreach. FAA also tasked an Aging Transport Systems Rule-making 

Advisory Committee to provide data, recommendations, and evaluation 

specifically on aging wiring systems. The new regulations being considered 

are entitled the Enhanced Airworthiness Program for Airplane Systems 

Rule and are expected by late-2005. Under this rule-making package, 

inspections would evaluate the health of wiring and all of its components 

for operation, such as connectors and clamps. Part of the system includes 

visual inspections of all wiring within arm’s reach, enhanced by the use of 

hand-held mirrors. This improvement is expected to catch more wiring 

flaws than current visual inspection practices. Where visual inspections 

can not be assumed to detect damage, detailed inspections will be required. 

The logic process to establish proper inspections is called the Enhanced 

Zonal Analysis Procedure, which will be issued as an Advisory Circular. 

This procedure is specifically directed towards enhancing the maintenance 

programs for aircraft whose current program does not include tasks 

derived from a process that specifically considers wiring in all zones as the 

potential source of ignition of a fire. 

Additional development and testing will be required before advanced arc 

fault circuit breakers will be available for use on aircraft. The FAA 

currently is in the midst of a prototype program where arc fault circuit 

breakers are installed in an anticollision light system on a major air 

carrier’s Boeing 737. The FAA and the Navy are currently analyzing tests of 

the circuit breakers to assess their reliability. The Society of Automotive 

Engineers is in the final stages of developing a Minimum Operating 

Performance Specification for the arc fault circuit breaker. 

Multisensor Detectors


Background	 Multisensor detectors, or “electronic noses,” could combine one or more 

standard smoke detector technologies; a variety of sensors for detecting 

such gases as carbon monoxide, carbon dioxide, or hydrocarbon; and a 

thermal sensor to more accurately detect and locate overheated or burning 

materials. The sensors could improve existing fire detection by discovering 

and locating potential or actual fires sooner and reducing the incidence of 

false alarms. These “smart” sensors would ignore the “nuisance sources” 

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such as dirt, dust, and condensation that are often responsible for 

triggering false alarms in existing systems.10 

According to studies by FAA and the National Institute of Standards and 

Technology, many current smoke and fire detection systems are not 

reliable. A 2000 FAA study indicated that cargo compartment detection 

systems, for example, resulted in at least one false alarm per week from 

1988 through 1990 and a 200:1 ratio of false alarms to actual fires in the 

cargo compartment from 1995 through 1999. 11 FAA has since estimated a 

100:1 cargo compartment false alarm ratio, partly because reported actual 

incidents have increased According to FAA’s Service Difficulty Report 

database,12 about 990 actual smoke and fire events were reported for 

2001.

13 

Multisensor detectors could be wired or wireless and linked to a 

suppression system. One or several sensor signals or indicators could 

cause the crew to activate fire extinguishers in a small area or zone, a 

larger area, or an entire compartment, resulting in a more appropriate and 

accurate use of the fire suppressant. For example, in areas such as the 

avionics compartment, materials that can burn are relatively well-defined. 

Multisensor detectors the size of a postage stamp could be designed to 

detect smoldering fires in cables or insulation or in overheated equipment 

in that area. Placing the detectors elsewhere in the airplane could improve 

the crew’s ability to respond to smoke or fire, including occurrences in 

hidden or inaccessible areas. 

Improved sensor detection technologies would both enhance safety by 

increasing crews’ confidence in the reliability of alarms and reduce costs 

by avoiding the need to divert aircraft in response to false alarms. One 

10One type of smart sensor would analyze the light-scattering properties of the particles in 

the air to differentiate between smoke particles and nuisance sources. 

11Aircraft Cargo Compartment Smoke Detector Alarm Incidents on U.S.-Registered 

Aircraft, 1974-1999, DOT/FAA/AR-TN00/29 (Washington, D.C.: June 2000). The study 

indicated a generally increasing number of false alarms as the size of the fleet grew. 

12Operating requirements for all aircraft have been amended by a 2000 final rule, whose 

deadline was recently extended for the third time, to report the occurrence or detection of 

failures, malfunctions, or defects concerning fire warning systems and false warnings of fire 

or smoke in the entire U.S. fleet. 

13According to FAA fire safety experts, most of these are contaminated air or smoke events 

in the cabin, detected by people, not by detectors. 

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study estimated the average cost of a diversion at $50,000 for a wide-body 

airplane and $30,000 for a narrow-body airplane. A diversion can also 

present safety concerns because of the possible increased risk of an 

accident and injuries to passengers and crew if there is (1) an emergency 

evacuation, (2) a landing at an unfamiliar airport, (3) a change to air traffic 

patterns, (4) a shorter runway, (5) inferior fire-fighting capability, (6) a loss 

of cargo load, or (7) inferior navigation aids. In 2002, 258 unscheduled 

landings due to smoke, fire, or fumes occurred. In addition, 342 flights were 

interrupted; some of these flights had to return to the gate or abort a 

takeoff. 

FAA established basic detector performance requirements in 1965 and 

1980. Detectors were to be made and installed in a manner that ensured 

their ability to resist, without failure, all vibration, inertia, and other loads 

to which they might normally be subjected; they also had to be unaffected 

by exposure to fumes, oil, water, or other fluids. Regulations in 1986 and 

1998 further defined basic location and performance requirements for 

detectors in different areas of the cargo compartment. In 1998, FAA issued 

a requirement for detection and extinguishment systems for one class of 

cargo compartments, which relied on oxygen starvation to control fires. 

This requirement significantly increased the number of detectors in use. 

Status	 Multisenor detectors are not currently available because additional 

research is needed. Although they have been demonstrated in the 

laboratory and on the ground, they have not been flight-tested. FAA and 

NASA have multisensor detector research and development efforts under 

way and are working to develop “smart” sensors and criteria for their 

approval. FAA will also finish revising an Advisory Circular that establishes 

test criteria for detection systems, designed to ensure that they respond to 

fires, but not to nonfire sources. In addition, several companies currently 

market “smart” detectors, mostly for nonaviation applications. For 

example, thermal detection systems sense and count certain particles that 

initially boil off the surface of smoldering or burning material. 

A European consortium has been developing a system, FIREDETEX, that 

combines the use of multisensor detectors, onboard fuel tank inerting, and 

water-mist-plus-nitrogen fire suppression systems for commercial 

airplanes. This program and associated studies are still ongoing and flight 

testing is planned for the last quarter of calendar year 2003. The results of 

tests on this system are expected to be made public in early 2004, and will 

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help to clarify the possible costs, benefits, and drawbacks of the combined 

system. 

Additional research, development, and testing will be required before 

multisensor technology is ready for use in commercial aviation. NASA, 

FAA, and private companies are pursuing various approaches. Some 

experts believe that some forms of multisensor technology could be in use 

in 5 years. When these units become available, questions may arise about 

where their use will be required. For example, the Canadian Transportation 

Safety Board has recommended that some areas in addition to those 

currently designated as fire zones may need to be equipped with 

detectors.14 These include the electronics and equipment bay (typically 

below the floor beneath the cockpit and in front of the passenger cabin), 

areas behind interior wall panels in the cockpit and cabin areas, and areas 

behind circuit breaker and other electronic panels. 

Water Mist Fire 

Suppression 

Background	 For over two decades, the aviation industry has evaluated the use of 

systems that spray water mist to suppress fires in airliner cabins, cargo 

compartments, and engine casings (see fig. 7). This effort was prompted, in 

part, by a need to identify an alternative to Halon, the primary chemical 

used to extinguish fires aboard airliners. With few exceptions, Halon is the 

sole fire suppressant installed in today’s aircraft fire suppression systems. 

However, the production of Halon was banned under the 1987 Montreal 

Protocol on Substances that Deplete the Ozone Layer, and its use in many 

noncritical sectors has been phased out. Significant reserves of Halon 

remain, and its use is still allowed in certain “critical use” applications, 

such as aerospace,15 because no immediate viable replacement agent 

14This recommendation was one of several resulting from the Canadian Transportation 

Safety Board’s investigation of the Swissair Flight 111 crash. 

15A use is considered “critical” when a need exists to protect against fire or explosion risks 

in areas that would result in a serious threat to essential services or pose an unacceptable 

threat to life, the environment, or national security. Typical critical users are aerospace, 

certain petrochemical production processors, certain marine applications, and national 

defense. 

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exists. To enable the testing and further development of suitable 

alternatives to and substitutes for Halon, FAA has drafted detailed 

standards for replacements in the cargo and engine compartments. These 

standards typically require replacement systems to provide the same level 

of safety as the currently used Halon extinguishing system. 

Figure 7: Water Mist Nozzle and Possible Placement 

According to FAA and others in the aviation industry, successful water mist 

systems could provide benefits against an in-flight or postcrash fire, 

including 

•	 cooling the passengers, cabin surfaces, furnishings and overall cabin 

temperatures; 

• decreasing toxic smoke and irritant gases; and 

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• delaying or preventing “flashover” fires from occurring. 16 

In addition, a 1996 study prepared for the British Civil Aviation Authority 

examined 42 accidents and 32 survivability factors and found that cabin 

water spray was the factor that showed the greatest potential for reducing 

fatality and injury rates.17 In the early 1990s, a joint FAA and Civil Aviation 

Authority study found that cabin water mist systems would be highly 

effective in improving survivability during a postcrash fire.18 However, the 

cost of using these systems outweighed the benefits, largely because of the 

weight of the water that airliners would be required to carry to operate 

them. In the mid- and late-1990s, FAA and others began examining water 

mist systems in airliner cargo compartments to help offset the cost of a 

cabin water mist system because the water could be used or shared by both 

the cargo compartment and the cabin. European and U.S. researchers also 

designed systems that required much less water because they targeted 

specific zones within an aircraft to suppress fires rather than spraying 

water throughout the cabin or the cargo compartment. 

In 2000, Navy researchers found a twin-fluid system to be highly reliable 

and maintenance-free.19 Moreover, this system’s delivery nozzles could be 

installed without otherwise changing cabin interiors. The Navy 

researchers’ report recommended that FAA and NTSB perform follow-up 

testing leading to the final design and certification of an interior water mist 

fire suppression system for all passenger and cargo transport aircraft. Also 

in 2000, a European consortium began a collaborative research project 

16Flashover can occur in an airplane cabin fire when all exposed combustible surfaces reach 

ignition temperature more or less simultaneously. It is characterized by rapid increases in 

temperature, with smoke, toxic gases, and oxygen depletion creating a largely 

nonsurvivable environment. 

17R.G.W. Cherry & Associates, Analysis of Structural Factors Influencing the Survivability 

of Occupants in Aeroplane Accidents, Civil Aviation Authority, Paper 96011 (London: 

December 1996). 

18Increasing the Survival Rate in Aircraft Accidents: Impact Protection, Fire 

Survivability, and Evacuation, European Transport Safety Council (December 1996). 

19Twin-fluid systems use air, nitrogen, or another gas in combination with water. They 

require lower water supply pressure and bigger nozzle orifices. 

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called FIREDETEX, which combines multisensor fire detectors, water 

mist, and onboard fuel tank inerting into one fire detection and suppression 

system.20 

In 2001 and 2002, FAA tested experimental mist systems to determine what 

could meet its preliminary minimum performance standards for cargo 

compartment suppression systems. A system that combines water mist 

with nitrogen met these minimum standards. In this system, water and 

nitrogen “knock down” the initial fire, and nitrogen suppresses any deepseated residual fire by inerting the entire compartment.21 In cargo 

compartment testing, this system maintained cooler temperatures than had 

either a plain water mist system or a Halon-based system. 

Status	 Additional research and testing are needed before water mist technology 

can be considered for commercial aircraft. For example, the weight and 

relative effectiveness of any water mist system would need to be 

considered and evaluated. In addition, before it could be used in aircraft, 

the consequences of using water will need to be further evaluated. For 

example, Boeing officials noted that using a water mist fire suppression 

system in the cabin in a post crash fire might actually reduce passenger 

safety if the mist or fog creates confusion among the passengers, leading to 

longer evacuation times. Further, of concern is the possible shorting of 

electrical wiring and equipment and damage to aircraft interiors (e.g., seats, 

entertainment equipment, and insulation). Water cleanup could also be 

difficult and require special drying equipment. 

20Inerting involves reducing flammability in fuel tanks, which is discussed separately in this 

report. 

21Boeing commented that this more recent system would not pass the original cargo 

minimum performance standard, and Boeing disagrees with FAA’s relaxing of the original 

standard. 

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Fire-Safe Fuels


Background	 Burning fuel typically dominates and often overwhelms postcrash fire 

scenarios and causes even the most fire-resistant materials to burn.22 Fuel 

spilled from tanks ruptured upon crash impact often forms an easily 

ignitable fuel-air mixture. A more frequent fuel-related problem is the fuel 

tank explosion, in which a volatile fuel-air mixture inside the fuel tank is 

ignited, often by an unknown source. For example, it is believed that fuel 

tank explosions destroyed a Philippines Air 737 in 1990, TWA Flight 800 in 

1996, and a Thai Air 737 in 2001. Therefore, reducing the flammability of 

fuel could improve survivability in postcrash fires as well as reduce the 

occurrence of fuel tank explosions. 

Reducing fuel flammability involves limiting the volatility23 of fuel and the 

rate at which it vaporizes.24 Liquid fuel can burn only when enough fuel 

vapor is mixed with air. If the fuel cannot vaporize, a fire cannot occur. This 

principle is behind the development of higher-flashpoint fuel, whose use 

can decrease the likelihood of a fuel tank explosion. The flash point is the 

lowest temperature at which a liquid fuel produces enough vapor to ignite 

in the presence of a source of ignition—the lower the flash point, the 

greater the risk of fire. If the fuel is volatile enough, however, and air is 

sucked into the fuel tank area upon crash impact, limiting the fuel’s 

vaporization can prevent a burnable mixture from forming. This principle 

supports the use of additives that modify the viscosity of fuel to limit 

postcrash fires; for example, antimisting kerosene contains such additives. 

22An average widebody aircraft carries 50,000 gallons of aviation fuel at takeoff. 

23Fuels function by releasing combustible gases. Indicators of volatility include a fuel’s 

boiling point (the higher the boiling point, the less volatile the fuel) and vapor pressure (the 

higher the vapor pressure, the more volatile the fuel). Therefore, raising the temperature 

can increase volatility. A highly volatile fuel is more likely to form a flammable or explosive 

mixture with air than a nonvolatile fuel. By definition, gases are volatile. Liquid fuels either 

are sufficiently volatile at room temperature to produce combustible vapor (ethanol, petrol) 

or they produce sufficient combustible vapors when heated (kerosene). 

24The fuel vaporization rate is the minimum temperature to which the pure liquid fuel must 

be heated so that the vapor pressure is high enough for an explosive mixture to be formed 

with air--then the liquid is allowed to evaporate and is brought into contact with a flame, 

spark, or hot filament. Flash points are lower than ignition temperatures. 

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According to FAA and NASA, however, these additives do nothing to 

prevent fuel tank explosions. 

From the early 1960s to the mid-1980s, FAA conducted research on fuel 

safety. The Aviation Safety Act of 1988 required that FAA undertake 

research on low-flammability aircraft fuels, and, in 1993, FAA developed 

plans for fuel safety research. In 1996, a National Research Council experts’ 

workshop on aviation fuel summarized existing fuel safety research efforts. 

The participants concluded that although postcrash fuel-fed aircraft fires 

had been researched, limited progress had been achieved and little work 

had been published. 

As part of FAA’s research, fuels have been modified with thickening 

polymer additives to slow down vaporization in crashes. Participants in 

the 1996 National Research Council workshop identified several long-term 

research goals for consideration in developing modified fuels and fuel 

additives to improve fire safety. They also agreed that a combination of 

effective fire-safe fuel additives could probably be either selected or 

designed, provided that fuel performance requirements were identified in 

advance. In addition, they agreed that existing aircraft designs that reduce 

the chance of fuel igniting do not present major barriers to the 

implementation of a fire-safe fuel. 

A 1996 European Transport Safety Council report suggested that 

antimisting kerosene be at least partially tested on regular military 

transport flights (e.g., in one tank, feeding one engine) to demonstrate its 

operational compatibility. The report also recommended the consideration 

of a study comparing the costs of the current principal commercial fuel and 

the special, higher-flashpoint fuel used by the Navy. According to NASA and 

FAA fire-safe fuels experts, military fuel is much harder to burn in storage 

or to ignite in a pan because of its lower volatility; however, it is just as 

flammable as aviation fuel when it is sprayed into an engine combustor. 

Status	 Fire-safe fuels are not currently available and are in the early stages of 

research and development. In January 2002, NASA opened a fire-safe fuels 

research branch at its Glenn Research Center in Ohio. NASA-Glenn is 

conducting aviation fuel research that evaluates fuel vapor flammability in 

conjunction with FAA’s fuel tank inerting program, including the 

measurement of fuel “flash points.” NASA is examining the effects of 

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surfactants, gelling agents, and chemical composition changes on the 

vaporization and pressure characteristics of jet fuel.25 

In addition to FAA’s and NASA’s research, some university and industry 

researchers have made progress in developing fire-safe fuels. Many use 

advanced analytical, computational modeling technologies to inform their 

research. A council of producers and users of fuels is also coordinating 

research on ways to use such fuels. NASA fuel experts remain optimistic 

that small changes in fuel technologies can have a big impact on fuel safety. 

Developing fire-safe fuels will require much more research and testing. 

There are significant technical difficulties associated with creating a fuel 

that meets aviation requirements while meaningfully decreasing the 

flammability of the fuel. 

Thermal Acoustic 

Insulation Materials 

Background 	 To keep an airplane quieter and warmer, a layer of thermal acoustic 

insulation material is connected to paneling and walls throughout the 

aircraft. This insulation, if properly designed, can also prevent or limit the 

spread of an in-flight fire. In addition, thermal acoustic insulation provides 

a barrier against a fire burning through the cabin from outside the 

airplane’s fuselage (See fig. 8.). Such a fire, often called a postcrash fire, 

may occur when fuel is spilled on the ground after a crash or an impact. 

25A surfactant, or surface-active agent, is a soluble compound that reduces the surface 

tension of liquids, or reduces interfacial tension between two liquids or a liquid and a solid. 

A gelling agent is a fuel “thickener.” 

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Figure 8: Fire Insulation Blankets 

While this thermal acoustic insulation material could help prevent the 

spread of fire, some of the insulation materials that have been used in the 

past have contributed to fires. For example, FAA indicated that an 

insulation material, called metallized Mylar®, contributed to at least six inflight fires. Airlines have stopped using this material and are removing it 

from existing aircraft. 

FAA’s two main efforts in this area are directed toward preventing fatal inflight fire and improving postcrash fire survivability. 

•	 Since 1998, FAA has been developing test standards for preventing inflight fires in response to findings that fire spread on some thermal 

acoustic insulation blanket materials. In 2000, FAA issued a notice of 

proposed rule-making that outlined new flammability test criteria for inflight fires. FAA’s in-flight test standards require thermal acoustic 

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insulation materials to protect passengers. According to the standards, 

insulation materials installed in airplanes will not propagate a fire if 

ignition occurs. 

•	 FAA is also developing more stringent burnthrough test standards for 

postcrash fires. FAA has been studying the penetration of the fuselage 

by an external fire—known as fuselage burnthrough—since the late 

1980s and believes that improving the fire resistance of thermal acoustic 

insulation could delay fuselage burnthrough. In laboratory tests 

conducted from 1999 through 2002, an FAA-led working group 

determined that insulation is the most potentially effective and practical 

means of delaying the spread of fire or creating a barrier to burnthrough. 

In 2002, FAA completed draft burnthrough standards outlining a 

proposed methodology for testing thermal acoustic insulation. The 

burnthrough standards would protect passengers and crews by 

extending by at least 4 minutes the time available for evacuation in a 

postcrash fire. 

Various studies have estimated the potential benefits from both test 

standards: 

•	 A 1999 study of worldwide aviation accidents from 1966 through 1993 

estimated that about 10 lives per year would have been saved if 

protection had provided an additional 4 minutes for occupants to exit 

the airplane. 

•	 A 2000 FAA study estimated that about 37 U.S. fatalities would be 

avoided between 2000 and 2019 through the implementation of both 

proposed standards.26 

•	 A 2002 study by the British Civil Aviation Authority of worldwide 

aviation accidents from 1991 through 2000 estimated that at least 34 

lives per year would have been saved if insulation had met both 

proposed standards. 

26FAA’s benefit estimate, based on $2.7 million per life saved, ranges from $37.7 million to 

$231.5 million, discounted to present value, based partially on 37.2 deaths avoided from its 

2000 study. FAA could not quantify benefits from flame propagation requirements, but 

indicated that avoiding an accident with 169 passenger fatalities would avert a $231.5 

million loss (not including the cost of the plane). 

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Status	 Insulation designed to replace metallized Mylar® is currently available. A 

2000 FAA airworthiness directive gave the airlines 5 years to remove and 

replace metallized Mylar® insulation in 719 affected airplanes. 

Replacement insulation is required to meet the in-flight standard and will 

be installed in these airplanes by mid-2005. In that airworthiness directive, 

FAA indicated that it did not consider other currently installed insulation to 

constitute an unsafe condition. 

Thermal acoustic insulation is currently available for installation on 

commercial airliners. This insulation has been demonstrated to reduce the 

chance of fatal in-flight fires and to improve postcrash fire survivability. On 

July 31, 2003, FAA issued a final rule requiring that after September 2, 2005, 

all newly manufactured airplanes having a seating capacity of more than 20 

passengers or over 6,000 pounds must use thermal acoustic insulation that 

meets more stringent standards for how quickly flames can spread.27 In 

addition, for aircraft of this size manufactured before September 2, 2003, 

replacement insulation in the fuselage must also meet the new, higher 

standard. 

Research is continuing to develop thermal acoustic insulation that provides 

better in-flight and burnthrough protection. Even when this material is 

available, the high cost of retrofitting airplanes may limit its use to newly 

manufactured aircraft. For example, FAA estimates that the metallized 

Mylar® retrofit alone will cost a total of $368.4 million, discounted to 

present value terms, for the 719 affected airplanes. Because thermal 

acoustic insulation is installed throughout the pressurized section of the 

airplane for the life of its service, retrofitting the entire fleet would cost 

several billion dollars. 

Ultra-Fire-Resistant 

Polymers 

Background	 Polymers are used in aircraft in the form of lightweight plastics and 

composites and are selected on the basis of their estimated installed cost, 

27Improved Flammability Standards for Thermal/Acoustic Insulation Materials Used in 

Transport Category Airplanes; Final Rule, FAA/DOT (14 C.F.R. parts 25, 91, et al.). 

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weight, strength, and durability. Most of the aircraft cabin is made of 

polymeric material. In the event of an in-flight or a postcrash fire, the use of 

polymeric materials with reduced flammability could give passengers and 

crew more time to evacuate by delaying the rate at which the fire spreads 

through the cabin. 

FAA researchers are developing better techniques to measure the 

flammability of polymers and to make polymers that are ultra fire resistant. 

Developing these materials is the long-term goal of FAA’s Fire Research 

Program, which, if successful, will “eliminate burning cabin materials as a 

cause of death in aircraft accidents.” Materials being improved include 

composite and adhesive resins, textile fibers, rubber for seat cushions, and 

plastics for molded parts used in seats and passenger electronics. (See fig. 

9.) 

Figure 9: Flammable Cabin Materials and Small-scale Material Test Device 

Adding flame-retardant substances to existing materials is one way to 

decrease their flammability. For example, some manufacturers add 

substances that release water when they reach a high temperature. When a 

material, such as wiring insulation, is heated or burns, the water acts to 

absorb the heat and cools down the fire. Other materials are designed to 

become surface-scorched on exposure to fire, causing a layer of char to 

protect the rest of the material from burning. Lastly, adding a type of clay 

can have a flame-retardant effect. In general, these fire-retardant polymers 

are formulated to pass an ignition test but do not meet FAA’s criterion for 

ultra fire resistance, which is a 90 percent reduction in the rate at which the 

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untreated material would burn. To meet this strict requirement, FAA is 

developing new “smart” polymers that are typical plastics under normal 

conditions but convert to ultra-fire-resistant materials when exposed to an 

ignition source or fire. 

FAA has adopted a number of flammability standards over the last 30 years. 

In 1984, FAA passed a retrofit rule that replaced 650,000 seat cushions with 

flame-retardant seat cushions at a total cost of about $75 million. The 

replacement seat cushions were found to delay cabin flashover by 40 to 60 

seconds. Fire-retardant seat cushions can also prevent ramp and in-flight 

fires that originate at a seat and would otherwise burn out of control if left 

unattended. In 1986 and 1988, FAA set maximum allowable levels of heat 

and smoke from burning interior materials to decrease the amount of 

smoke that they would release in a postcrash fire. These standards affected 

paneling in all newly manufactured aircraft. Airlines and airframe 

manufacturers invested several hundred million dollars to develop these 

new panels. 

Status	 Ultra-fireresistant polymers are not currently available for use on 

commercial airliners. These polymers are still in the early stages of 

research and development. To reduce the cost and simplify the testing of 

new materials, FAA is employing a new technique to characterize the 

flammability and thermal decomposition of new products; this technique 

requires only a milligram of sample material. The result has been the 

discovery of several new compositions of matter (including “smart” 

polymers). The test identifies key thermal and combustion properties that 

allow rapid screening of new materials.28 From these materials, FAA plans 

to select the most promising and work with industry to make enough of the 

new polymers to fabricate full-scale cabin components like sidewalls and 

stowage bins for fire testing. 

FAA’s phased research program includes the selection in 2003 of a small 

number of resins, plastics, rubbers, and fibers on the basis of their 

functionality, cost, and potential to meet fire performance guidelines. In 

2005, FAA plans to fabricate decorative panels, molded parts, seat 

cushions, and textiles for testing from 2007 through 2010. Full-scale testing 

28These methods test the heat release rate, total heat of combustion of the volatiles, thermal 

stability, char yield, decomposition process, and rate of decomposition. 

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is scheduled for 2011 but is contingent upon the availability of program 

funds and commercial interest from the private sector. 

Research continues on ultra-fire-resistant polymers that will increase 

protection against in-flight fires and cabin burnthrough. According to an 

FAA fire research expert, issues facing this research include (1) the current 

high cost of ultra-fire-resistant polymers; (2) difficulties in producing ultrafire-resistant polymers with low to moderate processing temperatures, 

good strength and toughness, and colorability and colorfastness; and (3) 

gaps in understanding the relationship between material properties and fire 

performance and between chemical composition and fire performance, 

scaling relationships, and fundamental fire-resistance mechanisms. In 

addition, once the materials are developed and tested, getting them 

produced economically and installed in aircraft will become an issue. It is 

expected that such new materials with ultra fire resistance would be more 

expensive to produce and that the market for such materials would be 

uncertain. 

Airport Rescue and 

Fire-Fighting 

Operations 

Background	 Because of the fire danger following a commercial airplane crash, having 

airport rescue and fire-fighting operations available can improve the 

chances of survival for the people involved. Most airplane accidents occur 

during takeoff or landing at the airport or in the surrounding community. A 

fire outside the airplane, with its tremendous heat, may take only a few 

minutes to burn through the airplane’s outside shell. According to FAA, 

firefighters are responsible for creating an escape path by spraying water 

and chemicals on the fire to allow the passengers and crew to evacuate the 

airplane. Firefighters use one or more trucks to extinguish external fires, 

often at great personal risk, and use hand-held attack lines when 

attempting to put out fires within the airplane fuselage. (See fig. 10). Fires 

within the fuselage are considered difficult to control with existing 

equipment and procedures because they involve complex conditions, such 

as smoke-laden toxic gases and high temperatures in the passenger cabin. 

FAA has taken actions to control both internal and external postcrash fires, 

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including requiring major airports to have airport rescue and fire-fighting 

operations. 

Figure 10: Airport Rescue and Fire Training 

In 1972, FAA first proposed regulations to ensure that major airports have a 

minimal level of airport rescue and fire-fighting operations. Some changes 

to these regulations were made in 1988. The regulations establish, among 

other things, equipment standards, annual testing requirements for 

response times, and operating procedures. The requirements depend on 

both the size of the airport and the resources the locality has agreed to 

make available as needed. 

In 1997, FAA compared airport rescue and fire-fighting missions and 

standards for civilian airports with DOD’s for defense installations and 

reported that DOD’s requirements were not applicable to civilian airports. 

In 1988, and again in 1998, Transport Canada Civil Aviation also studied its 

rescue and fire-fighting operations and concluded that the expenditure of 

resources for such unlikely occurrences was difficult to justify from a 

benefit-cost perspective. This conclusion highlighted the conflict between 

safety and cost in attempting to define rescue and fire-fighting 

requirements. 

A coalition of union organizations and others concerned about aviation 

safety released a report critical of FAA’s standards and operational 

regulations in 1999. According to the report, FAA’s airport rescue and firefighting regulations were outdated and inadequate. 

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Status	 In 2002, FAA incorporated measures recommended by NTSB into FAA’s 

Aeronautical Information Manual Official Guide to Basic Flight 

Information and Air Traffic Control Procedures.

29 These measures (1) 

designate a radio frequency at most major airports to allow direct 

communication between airport rescue and fire-fighting personnel and 

flight crewmembers in the event of an emergency and (2) specify a 

universal set of hand signals for use when radio communication is lost. 

In March 2001, FAA responded to the reports criticizing its airport rescue 

and fire-fighting standards by tasking its Aviation Regulatory Advisory 

Committee to review the agency’s rescue and fire-fighting requirements to 

identify measures that could be added, modified, or deleted. In 2003, the 

committee is expected to propose requirements for the number of trucks, 

the amount of fire extinguishing agent, vehicle response times, and staffing 

at airports and to publish its findings in a notice of proposed rule-making. 

Depending on the results of this FAA review, additional resources may be 

needed at some airports. The overall cost of improving airport rescue and 

fire-fighting response capabilities could be a significant barrier to the 

further development of regulations. For example, some in the aviation 

industry are concerned about the costs of extending requirements to 

smaller airports and of appropriately equipping all airports with resources. 

According to FAA, extending federal safety requirements to some smaller 

airports would cost at least $2 million at each airport initially and $1 million 

annually thereafter. 

29This manual is designed to provide the aviation community with basic flight information 

and air traffic control procedures for use in the National Airspace System of the United 

States. 

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Summaries of Potential Improved Evacuation 

Safety Advancements 

This appendix presents information on the background and status of 

potential advancements in evacuation safety that we identified, including 

the following: 

• improved passenger safety briefings; 

• exit seat briefings; 

• photo-luminescent floor track marking; 

• crewmember safety and evacuation training; 

• acoustic attraction signals; 

• smoke hoods; 

• exit slide testing; 

• overwing exit doors; 

• evacuation procedures for very large transport aircraft; and 

• personal flotation devices. 

Passenger Safety 

Briefings 

Background 	 Federal regulations require that passengers receive an oral briefing prior to 

takeoff on safety aspects of the upcoming flight. FAA also requires that oral 

briefings be supplemented with printed safety briefing cards that pertain 

only to that make and model of airplane and are consistent with the air 

carrier’s procedures. These two safety measures must include information 

on smoking, the location and operation of emergency exits, seat belts, 

compliance with signs, and the location and use of flotation devices. In 

addition, if the flight operates above 25,000 feet mean sea level, the briefing 

and cards must include information on the emergency use of oxygen. 

FAA published an Advisory Circular in March 1991 to guide air carriers’ 

development of oral safety briefings and cards. Primarily, the circular 

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defines the material that must be covered and suggests material that FAA 

believes should be covered. The circular also discusses the difficulty in 

motivating passengers to attend to the safety information and suggests 

making the oral briefing and safety cards as attractive and interesting as 

possible to increase passengers’ attention. The Advisory Circular suggests, 

for example, that flight attendants be animated, speak clearly and slowly, 

and maintain eye contact with the passengers. Multicolored safety cards 

with pictures and drawings should be used over black and white cards. 

Finally, the circular suggests the use of a recorded videotape briefing 

because it ensures a complete briefing with good diction and allows for 

additional visual information to be presented to the passengers. (See fig. 

11.) 

Figure 11: Airline Briefing to Passengers on Safety Briefing Cards 

Status 	 Despite efforts to improve passengers’ attention to safety information, a 

large percentage of passengers continue to ignore preflight safety briefings 

and safety cards, according to a study NTSB conducted in 1999. Of 457 

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passengers polled, 54 percent (247) reported that they had not watched the 

entire briefing because they had seen it before. An additional 70 passengers 

indicated that the briefing provided common knowledge and therefore 

there was no need to watch it. Of 431 passengers who answered a question 

about whether they had read the safety card, 68 percent (293) indicated 

that they had not, many of them stating that they had read safety cards on 

previous flights. 

Safety briefings and cards serve an important safety purpose for both 

passengers and crew. They are intended to prepare passengers for an 

emergency by providing them with information about the location and 

operation of exits and emergency equipment that they may have to 

operate—and whose location and operation may differ from one airplane 

to the next. Well-briefed passengers will be better prepared in an 

emergency, thereby increasing their chances of surviving and lessening 

their dependence on the crew for assistance. 

In its emergency evacuation study, NTSB recommended that FAA instruct 

airlines to “conduct research and explore creative and effective methods 

that use state-of-the-art technology to convey safety information to 

passengers.”1 NTSB further recommended “the presented information 

include a demonstration of all emergency evacuation procedures, such as 

how to open the emergency exits and exit the aircraft, including how to use 

the slides.” That research found that passengers often view safety briefings 

and cards as uninteresting and the information as intuitive. FAA has 

requested that commercial carriers explore different ways to present the 

materials to their passengers, adding that more should be done to educate 

passengers about what to do after an accident has occurred. 

Exit Seat Briefing


Background	 Passengers seated in an exit row may be called on to assist in an 

evacuation. Upon a crewmember’s command or a personal assessment of 

danger, these passengers must decide if their exit is safe to use and then 

open their exit hatch or door for use during an evacuation. In October 1990, 

1

NTSB, Safety Study: Emergency Evacuation of Commercial Airlines, [A-00-86] 

(Washington, D.C.: 2001). 

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FAA required airlines to actively screen passengers occupying exit seats for 

“suitability” and to administer one-on-one briefings on their 

responsibilities. This rule does not require specific training for exit seat 

occupants, but it does require that the occupants be duly informed of their 

distinct obligations. 

Status	 According to NTSB, preflight briefings of passengers in exit rows could 

contribute positively to a passenger evacuation. In a 1999 study, NTSB 

found that the individual briefings given to passengers who occupy exit 

seats have a positive effect on the outcome of an aircraft evacuation. The 

studies also found that as a result of the individualized briefings, flight 

attendants were better able to assess the suitability of the passengers 

seated in the exit seats. 

According to FAA’s Flight Standards Handbook Bulletin for Air 

Transportation, several U.S. airlines have identified specific cabin 

crewmembers to perform “structured personal conversations or briefings,” 

designed to equip and prepare passengers in exit seats beyond the general 

passenger briefing. Also, the majority of air carriers have procedures to 

assist crewmembers with screening passengers seated in exit rows. 

FAA’s 1990 rule requires that passengers seated in exit rows be provided 

with information cards that detail the actions to be taken in the case of an 

emergency. However, individual exit row briefings, such as those 

recommended by NTSB, are not required. Also included on the information 

cards are provisions for a passenger who does not wish to be seated in the 

exit row to be reseated. Additionally, carriers are required to assess the exit 

row passenger’s ability to carry out the required functions. The extent of 

discussion with exit row passengers depends on each airline’s policy. 

Photo-luminescent 

Floor Track Marking 

Background	 In June 1983, an Air Canada DC-9 flight from Dallas to Toronto was cruising 

at 33,000 feet when the crew reported a lavatory fire. An emergency was 

declared, and the aircraft made a successful emergency landing at the 

Cincinnati Northern Kentucky International Airport. The crew initiated an 

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evacuation, but only half of the 46 persons aboard were able to escape 

before becoming overcome by smoke and fire. In its investigation of this 

accident, NTSB learned that many of the 23 passengers who died might 

have benefited from floor tracking lighting. As a result, NTSB 

recommended that airlines be equipped with floor-level escape markings. 

FAA determined that floor lighting could improve the evacuation rate by 20 

percent under certain conditions, and FAA now requires all airliners to 

have a row of lights along the floor to guide passengers to the exit should 

visibility be reduced by smoke. 

On transport category aircraft, these escape markings, called floor 

proximity marking systems, typically consist primarily of small electric 

lights spaced at intervals on the floor or mounted on the seat assemblies, 

along the aisle. The requirement for electricity to power these systems has 

made them vulnerable to a variety of problems, including battery and 

wiring failures, burned-out light bulbs, and physical disruption caused by 

vibration, passenger traffic, galley cart strikes, and hull breakage in 

accidents. Attempts to overcome these problems have led to the proposal 

that nonelectric, photo-luminescent (glow-in-the-dark) materials be used in 

the construction of floor proximity marking systems. The elements of these 

new systems are “charged” by the normal airplane passenger cabin lighting, 

including the sunlight that enters the cabin when the window shades are 

open during daylight hours. (See fig. 12.) 

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Figure 12: Floor Track Marking Using Photo-luminescent Materials 

Status	 Floor track marking using photo-luminescent materials is currently 

available but not required for U.S. commercial airliners. Performance 

demonstrations of photo-luminescent technology have found that 

strontium aluminate photo-luminescent marking systems can be effective 

in providing the guidance for egress that floor proximity marking systems 

are intended to achieve. According to industry and government officials, 

such photo-luminescent marking systems are also cheaper to install than 

electric light systems and require little to no maintenance. Moreover, 

photo-luminescent technology weighs about 15 to 20 pounds less than 

electric light systems and, unlike the electric systems, illuminates both 

sides of the aisle, creating a pathway to the exits. 

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Photo-luminescent floor track marking technology is mature and is 

currently being used by a small number of operators, mostly in Europe. In 

the United States, Southwest Airlines has equipped its entire fleet with the 

photo-luminescent system. However, the light emitted from photoluminescent materials is not as bright as the light from electrically operated 

systems. Additionally, the photo-luminescent materials are not as effective 

when they have not been exposed to light for an extended period of time, 

as after a long overseas nighttime flight. The estimated retail price of an 

entire system, not including the installation costs, is $5,000 per airplane. 

Crewmember Safety 

and Evacuation 

Training 

Background	 FAA requires crewmembers to attend annual training to demonstrate their 

competency in emergency procedures. They have to be knowledgeable and 

efficient while exercising good judgment. Crewmembers must know their 

own duties and responsibilities during an evacuation and be familiar with 

those of their fellow workers so that they can take over for others if 

necessary. 

The requirements for emergency evacuation training and demonstrations 

were first established in 1965. Operators were required to conduct fullscale evacuation demonstrations, include crewmembers in the 

demonstrations, and complete the demonstrations in 2 minutes using 50 

percent of the exits. The purpose of the demonstrations was to test the 

crewmembers’ ability to execute established emergency evacuation 

procedures and to ensure the realistic assignment of functions to the crew. 

A full-scale demonstration was required for each type and model of 

airplane when it first started passenger-carrying operations, increased its 

passenger seating capacity by 5 percent or more, or underwent a major 

change in the cabin interior that would affect an emergency evacuation. 

Subsequently, the time allowed to evacuate the cabin during these tests was 

reduced to 90 seconds. 

The aviation community took steps in the 1990s to develop a program 

called Crew Resource Management that focuses on overall improvements 

in crewmembers’ performance and flight safety strategies, including those 

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for evacuation. FAA officials told us that they plan to emphasize the 

importance of effective communication between crewmembers and are 

considering updating a related Advisory Circular. Effective communication 

between cockpit and cabin crew are particularly important with the added 

security precautions being taken after September 11, 2001, including the 

locking the cockpit door during flight. 

Status	 The traditional training initiative now has an advanced curriculum, 

Advanced Crew Resource Management. According to FAA, this 

comprehensive implementation package includes crew resource 

management procedures, training for instructors and evaluators, training 

for crewmembers, a standardized assessment of the crew’s performance, 

and an ongoing implementation process. This advanced training was 

designed and developed through a collaborative effort between the airline 

and research communities. FAA considers training to be an ongoing 

development process that provides airlines with unique crew resource 

management solutions tailored to their operational demands. The design of 

crew resource management procedures is based on principles that require 

an emphasis on the airline’s specific operational environment. The 

procedures were developed to emphasize these crew resource 

management elements by incorporating them into standard operating 

procedures for normal as well as abnormal and emergency flight situations. 

Because commercial airliner accidents are rare, crewmembers must rely 

on their initial and recurrent training to guide their actions during an 

emergency. Even in light of advances and initiatives in evacuation 

technology, such as slides and slide life rafts, crewmembers must still 

assume a critical role in ensuring the safe evacuation of their passengers. 

Airline operators have indicated that it is very costly for them to pull large 

numbers of crewmembers off-line to participate in training sessions. 

FAA officials told us that improving flight and cabin crew communication 

holds promise for ensuring the evacuation of passengers during an 

emergency. To improve this communication and coordination between 

flight and cabin crew, FAA plans to update the related Advisory Circular, 

oversee training, and charge FAA inspectors with monitoring air carriers 

during flights to see that improvements are being implemented. In addition, 

FAA is enhancing its guidance to air carriers on preflight briefings for flight 

crews to sharpen their responses to emergency situations and mitigate 

passengers’ confusion. FAA expects this guidance to bolster the use and 

quality of preflight briefings between pilots and flight attendants on 

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security, communication, and emergency procedures. According to FAA, 

these briefings have been shown to greatly improve the flight crew’s safety 

mind-set and to enhance communication. 

Acoustic Attraction 

Signals 

Background	 Acoustic attraction signals make sounds to help people locate the doors in 

smoke, darkness, or when lights and exit signs are obscured. When 

activated, the devices are intended to help people to determine the 

direction and approximate distance of the sound—and of the door. 

Examples of audio attraction signals include recorded speech sounds, 

broadband multifrequency sounds (“white noise”), or alarm bells. 

Research to determine if acoustic attraction signals can be useful in aircraft 

evacuation has included, for example, FAA’s Civil Aeromedical Institute 

testing of recorded speech sounds in varying pitches, using phrases such as 

“This way out,” “This way,” and “Exit here.” Researchers at the University 

of Leeds developed Localizer Directional Sound beacons, which combine 

broadband, multifrequency “white noise” of between 40Hz and 20kHz with 

an alerting sound of at least one other frequency, according to the inventor 

(see fig. 13). 

Figure 13: Test Installation of Acoustic Signalling Device 

Note: Acoustic signaling device is of the type used near building exits. 

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The FAA study noted above of acoustic attraction signals found that in the 

absence of recorded speech signals, the majority of participants evacuating 

a low-light-level, vision-obscured cabin will head for the front exit or will 

follow their neighbors. In contrast, participants exposed to recorded 

speech sounds will select additional exits, even those in the rear of the 

airplane. During aircraft trials conducted by Cranfield University and 

University of Greenwich researchers, tests of directional sound beacons 

found that under cabin smoke conditions, exits were used most efficiently 

when the cabin crew gave directions and the directional sound beacons 

were activated. With this combination, the distribution of passengers to the 

available exits was better than with cabin crew directions alone, sound 

beacons alone, no cabin crew directions, or no sound beacons. 

Researchers found that passengers were able to identify and move toward 

the closest sound source inside the airplane cabin and to distinguish 

between two closely spaced loudspeakers. However, in 2001, Airbus 

conducted several evacuation test trials of audio attraction signals using an 

A340 aircraft. According to Airbus, the acoustic attraction signals did not 

enhance passengers’ orientation, and, overall, did not contribute to 

passengers’ safety. 

Status 	 While acoustic attraction signals are currently available, further research is 

needed to determine if their use is warranted on commercial airliners. FAA, 

Transport Canada Civil Aviation, and the British Civilian Aviation Authority 

do not currently mandate the use of acoustic attraction signals. The United 

Kingdom’s Air Accidents Investigation Branch made a recommendation 

after the fatal Boeing 737 accident at Manchester International Airport in 

1985 that research be undertaken to assess the viability of audio attraction 

signals and other evacuation techniques to assist passengers impaired by 

smoke and toxic or irritant gases. The Civilian Aviation Authority accepted 

the recommendation and sponsored research at Cranfield University; 

however, it concluded from the research results that the likely benefit of 

the technology would be so small that no further action should be taken, 

and the recommendation was closed in 1992. 

The French Direction Generale de l’Aviation Civile funded aircraft 

evacuation trials using directional sound beacons in November 2002, with 

oversight by the European Joint Aviation Authorities. The trials were 

conducted at Cranfield University’s evacuation simulator with British 

Airways cabin crew and examined eight trial evacuations by two groups of 

‘passengers.’ The study surveyed the participants’ views on various aspects 

of their evacuation experience and measured the overall time to evacuate. 

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The speed of evacuation was found to be biased by the knowledge 

passengers’ gained in the four successive trials, and by variations in the 

number of passengers participating on the 2 days (155 and 181). The four 

trials by each of the two groups of passengers also involved different 

combinations of crew and sound in each. The study concluded that the 

insufficient number of test sessions further contributed to bias in the 

results, and that further research would be needed to determine whether 

the devices help to speed overall evacuation. 

Further research and testing are needed before acoustic attraction signals 

can be considered for widespread airline use. The signals may have 

drawbacks that would need to be addressed. For example, the Civil 

Aviation Authority found that placing an audio signal in the bulkhead might 

disorient or confuse the first few passengers who have to pass and then 

move away from the sound source to reach the exit. Such hesitation slowed 

passengers’ evacuation during testing. The researchers at Cranfield 

University trials in 1990 concluded that an acoustic sound signal did not 

improve evacuation times by a statistically significant amount, suggesting 

that the device might not be cost-effective. 

Smoke Hoods 


Background	 Smoke hoods are designed to provide the user with breathable, filtered air 

in an environment of smoke and toxic gases that would otherwise be 

incapacitating. More people die from smoke and toxic gases than from fire 

after an air crash. Because only a few breaths of the dense, toxic smoke 

typically found in aircraft fires can render passengers unconscious and 

prevent their evacuation, the wider use of smoke hoods has been 

investigated as a means of preventing passengers from being overcome by 

smoke and of giving them enough breathable air to evacuate. However, 

some studies have found that smoke hoods are only effective in certain 

types of fires and in some cases may slow the evacuation of cabin 

occupants. 

As shown in figure 14, a filter smoke hood can be a transparent bag worn 

over the head that fits snugly at the neck and is coated with fire-retardant 

material; it has a filter but no independent oxygen source and can provide 

breathable air by removing some toxic contaminants from the air for a 

period ranging from several minutes to 15 minutes, depending on the 

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severity and type of air contamination. The hood has a filter to remove 

carbon monoxide—a main direct cause of death in fire-related commercial 

airplane accidents, as well as hydrogen cyanide—another common cause 

of death, sometimes from incapacitation that can prevent evacuation. 

Hoods also filter carbon dioxide, chlorine, ammonia, acid gases such as 

hydrogen chloride and hydrogen sulfide, and various hydrocarbons, 

alcohols, and other solvents. Some hoods also include a filter to block 

particulate matter. One challenge is where to place the hoods in a highly 

accessible location near each seat. 

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Figure 14: An Example of a Commercially Available Smoke Hood 

Certain smoke hoods have been shown to filter out many contaminants 

typically found in smoke from an airplane cabin fire and to provide some 

temporary head protection from the heat of fire. In a full-scale FAA test of 

cabin burnthrough, toxic gases became the driving factor determining 

survivability in the forward cabin, reaching lethal levels minutes before the 

smoke and temperature rose to unsurvivable levels. 

A collaborative effort to estimate the potential benefits of smoke hoods 

was undertaken in 1986 by the British Civil Aviation Authority (CAA), the 

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Federal Aviation Administration, the Direction Générale de l’Aviation Civile 

(France) and Transport Canada Civil Aviation. The resulting 1987 study 

examined the 20 accidents where sufficient data was available out of 74 

fire-related accidents worldwide from 1966 to 1985. The results were 

sensitive to assumptions regarding extent of use and delays due to putting 

on smoke hoods. The study concluded that smoke hoods could 

significantly extend the time available to evacuate an aircraft and would 

have saved approximately 179 lives in the 20 accidents studied, assuming 

no delay in donning smoke hoods. Assuming a 10 percent reduction in the 

evacuation rate due to smoke hood use would have resulted in an 

estimated 145 lives saved in the 20 accidents with adequate data. A 15 

second delay in donning the hoods would have saved an estimated 97 lives 

in the 20 accidents.2

 When the likelihood of use of smoke hoods was 

included in the analysis for each accident, the total net benefit was 

estimated at 134 lives saved in the 20 accidents. The study also estimated 

that an additional 228 lives would have been saved in the 54 accidents 

where less data was available, assuming no delay in evacuation.

3 

The U.S. Air Force and a major manufacturer are developing a drop-down 

smoke hood with oxygen. Because current oxygen masks in airplanes are 

not airtight around the mouth, they provide little protection from toxic 

gases and smoke in an in-flight fire. To provide protection from these 

hazards, as well as from decompression and postcrash fire and smoke, the 

Air Force’s drop-down smoke hood with oxygen uses the airplane’s existing 

oxygen system and can fit into the overhead bin of a commercial airliner 

where the oxygen mask is normally stowed. This smoke hood is intended 

to replace current oxygen masks but also be potentially separated from the 

oxygen source in a crash to provide time to evacuate. 

Status	 Smoke hoods are currently available and produced by several 

manufacturers; however, not all smoke hoods filter carbon monoxide. They 

are in use on many military and private aircraft, as well as in buildings. An 

2

These estimates assume 100 percent smoke hood use. The net 97 lives saved with a 15 

second delay assumes that smoke hoods would have saved lives in six accidents and cost 

lives in four; the net 145 lives saved with a 10 percent reduction in the evacuation rate 

assumes that smoke hoods would have saved lives in six accidents and cost lives in two. 

3

 “Smoke Hoods: Net Safety Benefit Analysis,” a collaborative effort by the Civil Aviation 

Authority, Federal Aviation Administration, Direction Générale de l’Aviation Civile, and 

Transport Canada, London, November 1987, CAA Paper 87017. 

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individually-purchased filter smoke hood costs about $70 or more, but 

according to one manufacturer bulk order costs have declined to about $40 

per hood. In addition, they estimated that hoods cost about $2 a year to 

install and $5 a year to maintain. They weigh about a pound or less and 

have to be replaced about every 5 years. Furthermore, airlines could incur 

additional replacement costs due to theft if smoke hoods were placed near 

passenger seats in commercial aircraft. 

Neither the British CAA, the FAA, the DGAC, nor Transport Canada Civil 

Aviation has chosen to require smoke hoods. The British Air Accident 

Investigations Branch recommended that smoke hoods be considered for 

aircraft after the 1985 Manchester accident, in which 48 of 55 passengers 

died on a runway from an engine fire before takeoff, mainly from smoke 

inhalation and the effects of hydrogen cyanide. Additionally, a U.K. 

parliamentary committee recommended research into smoke hoods in 

1999, and the European Transport Safety Council, an international 

nongovernmental organization whose mission is to provide impartial 

advice on transportation safety to the European Commission and 

Parliaments, recommended in 1997 that smoke hoods be provided in all 

commercial aircraft. Canada’s Transportation Safety Board has taken no 

official position on smoke hoods, but has noted a deficiency in cabin safety 

in this area and recommended further evaluation of voluntary passenger 

use. 

Although smoke hoods are currently available, they remain controversial. 

Passengers are allowed to bring filter type smoke hoods on an airplane, but 

FAA is not considering requiring airlines to provide smoke hoods for 

passengers. The debate over whether smoke hoods should be installed in 

aircraft revolves mainly around regulatory concerns that passengers will 

not be able to put smoke hoods on quickly in an emergency; that hoods 

might hinder visibility, and that any delay in putting on smoke hoods would 

slow down an evacuation. FAA’s and CAA’s evacuation experiments—to 

determine how long it takes for passengers to unpack and don smoke 

hoods and whether an evacuation would be slowed by their use—have 

reached opposite conclusions about the effects of smoke hoods on 

evacuation rates. The CAA has noted that delays in putting on smoke hoods 

by only one or two people could jeopardize the whole evacuation. An 

opposite view by some experts is that the gas and smoke-induced 

incapacitation of one or two passengers could also delay an evacuation. 

FAA believes that an evacuation might be hampered by passengers’ 

inability to quickly and effectively access and don smoke hoods, by 

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competitive passenger behavior, and by a lack of passenger attentiveness 

during pre-flight safety briefings. FAA noted that smoke hoods can be 

difficult to access and use even by trained individuals. However, other 

experts have noted that smoke hoods might reduce panic and help make 

evacuations more orderly, that competitive behavior already occurs in 

seeking access to exits in a fire, and that passengers could learn smoke 

hood safety procedures in the pre-flight safety briefings in the same way 

they learn to use drop-down oxygen masks or flotation devices. 

The usefulness of smoke hoods varies across fire scenarios depending on 

assumptions about how fast hoods could be put on and how much time 

would be available to evacuate. One expert told us that the time needed to 

put on a smoke hood might not be important in several fire scenarios, such 

as an in-flight fire in which passengers are seeking temporary protection 

from smoke until the airplane lands and an evacuation can begin. In other 

scenarios—a ground evacuation or postcrash evacuation — some experts 

argue that passengers in back rows or far from an exit may have their exit 

path temporarily blocked as other passengers exit and, because of the 

delay in their evacuation, may have a greater need and more time available 

to don smoke hoods than passengers seated near usable exits. 

Exit Slide Testing


Background	 Exit slide systems are rarely used during their operational life span. 

However, when such a system is used, it may be under adverse crash 

conditions that make it important for the system to work as designed. To 

prevent injury to passengers and crew escaping through floor-level exits 

located more than 6 feet above the ground, assist devices (i.e., slides or 

slide-raft systems) are used. (See fig. 15.) 

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Figure 15: Drawing of Possible Emergency Slide Testing of FAA’s 747 Test Aircraft 

The rapid deployment, inflation, and stability of evacuation slides are 

important to the effectiveness of an aircraft’s evacuation system, as was 

illustrated in the fatal ground collision of a Northwest Airlines DC-9 and a 

Northwest Airlines 727 in Romulus, Michigan, in December 1990. As a 

result of the collision, the DC-9 caught fire, but there were several slide 

problems that slowed the evacuation. For example, NTSB later found that 

the internal tailcone exit release handle was broken, thereby preventing the 

tailcone from releasing and the slide from deploying. 

Because of concerns about the operability of exit slides, NTSB 

recommended in 1974 that FAA improve its maintenance checks of exit 

slide operations. In 1983, FAA revised its exit slide requirements to specify 

criteria for resistance to water penetration and absorption, puncture 

strength, radiant heat resistance, and deployment as flotation platforms 

after ditching. 

Status	 All U.S. air carriers have an FAA-approved maintenance program for each 

type of airplane that they operate. These programs require that the 

components of an airplane’s emergency evacuation system, which includes 

the exit slides, be periodically inspected and serviced. An FAA principal 

maintenance inspector approves the air carrier’s maintenance program. 

According to NTSB, although most air carriers’ maintenance programs 

require that a percentage of emergency evacuation slides or slide rafts be 

tested for deployment, the percentage of required on-airplane deployments 

is generally very small. For example, NTSB found that American Airlines’ 

FAA-approved maintenance program for the A300 requires an on-airplane 

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operational check of four slides or slide rafts per year. Delta Air Lines’ FAAapproved maintenance program for the L-1011 requires that Delta activate a 

full set of emergency exits and evacuation slides or slide rafts every 24 

months. Under an FAA-approved waiver for its maintenance program, 

United is not required to deploy any slide on its 737 airplanes. 

NTSB also found that FAA allows American Airlines to include inadvertent 

and emergency evacuation deployments toward the accomplishment of its 

maintenance program; therefore, it is possible that American would not 

purposely deploy any slides or slide rafts on an A300 to comply with the 

deployment requirement during any given year. In addition, NTSB found 

that FAA also allows Delta Air Lines to include inadvertent and emergency 

evacuation deployments toward the accomplishment of its maintenance 

program. 

NTSB holds that because inadvertent and emergency deployments do not 

occur in a controlled environment, problems with, or failures in, the system 

may be more difficult to identify and record, and personnel qualified to 

detect such failures may not be present. For example, in an inadvertent or 

emergency slide or slide raft deployment, observations on the amount of 

time it takes to inflate the slide or slide raft, and the pressure level of the 

slide or slide raft are not likely to be documented. For these reasons, a 1999 

NTSB report said that FAA’s allowing these practices could potentially 

leave out significant details about the interaction of the slide or slide raft 

with the door or how well the crew follows its training mock-up 

procedures. Accordingly, in 1999, NTSB recommended that FAA stop 

allowing air carriers to count inadvertent and emergency deployments 

toward meeting their maintenance program requirement because 

conditions are not controlled and important information (on, for example, 

the interface between the airplane and the evacuation slide system, timing, 

durability, and stability) is not collected. The recommendation continues to 

be open at the NTSB. NTSB officials said they would be meeting to discuss 

this recommendation with FAA in the near future. 

Additionally, NTSB recommended that FAA, for a 12-month period, require 

that all operators of transport-category aircraft demonstrate the onairplane operation of all emergency evacuation systems (including the 

door-opening assist mechanisms and slide or slide raft deployment) on 10 

percent of each type of airplane (at least one airplane per type) in their 

fleets. NTSB said that these demonstrations should be conducted on an 

airplane in a controlled environment so that qualified personnel can 

properly evaluate the entire evacuation system. NTSB indicated that the 

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results of the demonstrations (including an explanation of the reasons for 

any failures) should be documented for each component of the system and 

should be reported to FAA.4 

Overwing Exit Doors 


Background	 Prompted by a tragedy in which 57 of the 137 people on board a British 

Airtours B-737 were killed because passengers found exit doors difficult to 

access and operate, the British Civil Aviation Authority initiated a research 

program to explore changes to the design of the overwing exit (Type III) 

door. 

Trained crewmembers are expected to operate most of the emergency 

equipment on an airplane, including most floor-level exit doors. But 

overwing exit doors, termed “self-help exits,” are expected to be and will 

primarily be opened by passengers without formal training.5

 NTSB reported 

that even when flight attendants are responsible for opening the overwing 

exit doors, passengers are likely to make the first attempt to open the 

overwing exit hatches because the flight attendants are not physically 

located near the overwing exits. 

There are now two basic types of overwing exit doors—the “self-help” 

doors that are manually removed inward and then stowed and the newer 

“swing out” doors that open outward on a hinge. 

According to NTSB, passengers continue to have problems removing the 

inward-opening exit door and stowing it properly. The manner in which the 

overwing exit is opened and how and where the hatch should be stowed is 

not intuitively obvious to passengers, nor is it easily or consistently 

depicted graphically. NTSB recently recommended to FAA that Type III 

overwing exits on newly manufactured aircraft be easy and intuitive to 

4

NTSB, Emergency Evacuation of Commercial Airplanes, 2001, [A-00-76] (Washington, 

D.C.:2000). 

5

The overwing exit hatch can weigh as much as 65 pounds and be 20 inches wide and 36 

inches high. 

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open and have automatic stowage out of the egress path.6 NTSB has 

indicated that the semiautomatic, fast-opening, Type III overwing exit 

hatch could give passengers additional evacuation time. 

Status	 Over-wing exit doors that “swing out” on hinges rather than requiring 

manual removal are currently available. The European Joint Aviation 

Authorities (JAA) has approved the installation of these outward-opening 

hinged doors on new-production aircraft in Europe. In addition, Boeing has 

redesigned the overwing exit door for its next-generation 737 series. This 

redesigned, hinged door has pressurized springs so that it essentially pops 

up and outward, out of the way, once its lever is pulled. The exit door 

handle was also redesigned and tested to ensure that anyone could operate 

the door using either single or double handgrips. Approximately 200 people 

who were unfamiliar with the new design and had never operated an 

overwing exit tested the outward-opening exit door. These tests found that 

the average adult could operate the door in an emergency. The design 

eliminates the problem of where to stow the exit hatch because the door 

moves up and out of the egress route. 

While the new swing-out doors are available, it will take some time for 

them to be widely used. Because of structural difficulties and cost, the new 

doors are not being considered for the existing fleet. For new-production 

airplanes, their use is mixed because JAA requires them in Europe for some 

newer Boeing 737s, but FAA does not require them in the United States. 

However, FAA will allow their use. As a result, some airlines are including 

the new doors on their new aircraft, while others are not. For example, 

Southwest Airlines has the new doors on its Boeing 737s. The extent to 

which other airlines and aircraft models will have the new doors installed 

remains to be seen and will likely depend on the cost of installation, the 

European market for the aircraft, and any additional costs to train flight 

attendants in its use. 

6

NTSB, Emergency Evacuation of Commercial Airplanes, [A-00-76] (Washington, D.C., 

2000). 

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Next Generation 

Evacuation Equipment 

and Procedures 

Background	 Airbus, a leading aircraft manufacturer, has begun building a family of A380 

aircraft, also called Large Transport Aircraft (see fig. 16). Early versions of 

the A380, which is scheduled to begin flight tests in 2005 and enter 

commercial service in 2006, will have 482 to 524 seats. The A380-800 

standard layout references 555 seats. Later larger configurations could 

accommodate up to 850 passengers. The A380 is designed to have 16 

emergency doors and require 16 escape slides, compared with the 747, 

which requires 12. Later models of the A380 could have 18 emergency exits 

and escape slides. 

Figure 16: Airbus’ Planned Double Deck Aircraft 

Status	 The advent of this type of Large Transport Aircraft is raising questions 

about how passengers will exit the aircraft in an emergency. The upper 

deck doorsill of the A380 will be approximately 30 feet above the ground, 

depending on the position (attitude) of the aircraft. According to an Airbus 

official responsible for exit slide design and operations, evacuation slides 

have to reach the ground at a safe angle even if the aircraft is tipped up; 

however, extra slide length is undesirable if the sill height is normal. 

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Previously, regulations would have required slides only to touch the ground 

in the tip-up case, even if that meant introduction of relatively steep sliding 

surfaces. However, because of the sill height, passengers may hesitate 

before jumping and their hesitation may extend the total evacuation time. 

Because some passengers may be reluctant to leap onto the slide when 

they can see how far it is to the ground, the design concept of the A380 

evacuation slides includes blinder walls at the exit and a curve in the slide 

to mask the distance to the ground. 

A next-generation evacuation system developed by Airbus and Goodrich 

called the “intelligent slide” is a possible solution to the problem of the 

Large Transport Aircraft’s slide length. The technology is not a part of the 

slide, but is connected to the slide through what is called a door 

management system composed of sensors. The “brains” of the technology 

will be located inside the forward exit door of the cabin, and the 

technology is designed to adjust the length of the slide according to the 

fuselage’s tipping angle to the ground. The longest upper-deck slide for an 

A380 could exceed 50 feet. 

The A380 slides are made of a nylon-based fabric that is coated with 

urethane or neoprene, and they are 10 percent lighter than most other 

slides on the market. They have to be packed tightly into small bundles at 

the foot of emergency exit doors and are required to be fully inflated in 6 

seconds. Officials at Airbus noted that the slides are designed to withstand 

the radiant heat of a postimpact fire for 180 seconds, compared with the 90 

seconds required by regulators. 

According to a Goodrich official, FAA will require Goodrich to conduct 

between 2,000 and 2,500 tests on the A380 slides to make sure they can 

accommodate a large number of passengers quickly and withstand wind, 

rain, and other weather conditions. The upper-level slides, which are wide 

enough for two people, have to enable the evacuation of 140 people per 

minute, according to Airbus officials. An issue to be resolved is whether a 

full-scale demonstration test will be required or whether a partial test using 

a certain number of passengers, supplemented by a computer simulation of 

an evacuation of 555 passengers, can effectively demonstrate an 

evacuation from this type of aircraft. Airbus officials told us that a full-scale 

demonstration could result in undesirable injuries to the participants and is 

therefore not the preferred choice. 

Officials at the Association of Flight Attendants have expressed concern 

that there has not been a full-scale evacuation demonstration involving the 

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A380. They are concerned that computer modeling might not really match 

the human experience of jumping onto a slide from that height. In addition, 

they are concerned that other systems involved in emergency exiting, such 

as the communication systems, need to be tested under controlled 

conditions. As a result, they believe a full-scale demonstration under the 

current 90-second standard is necessary. 

Personal Flotation 

Devices 

Background	 All commercial aircraft that fly over water more than 50 nautical miles from 

the nearest shore are required to be equipped with flotation devices for 

each occupant of the airplane. According to FAA, 44 of the 50 busiest U.S. 

airports are located within 5 miles of a significant body of water. In 

addition, life vests, seat cushions, life rafts, and exit slides may be used as 

flotation devices for water emergencies. 

FAA policies dictate that if personal flotation devices are installed beneath 

the passenger seats of an aircraft, the devices must be easily retrievable. 

Determinations of compliance with this requirement are based on the 

judgment of FAA as the certifying authority. 

Status	 FAA is conducting research and testing on the location and types of 

flotation devices used in aircraft. When it has completed this work, it is 

likely to provide additional guidance to ensure that the devices are easily 

retrievable and usable. FAA’s research is designed to analyze human 

performance factors, such as how much time passengers need to retrieve 

their vests, whether and how the cabin environment physically interferes 

with their efforts, and how physically capable passengers are of reaching 

their vests while seated and belted. FAA is reviewing four different life vest 

installation methods and has conducted tests on 137 human subjects. 

According to an early analysis of the data, certain physical installation 

features significantly affect both the ability of a typical passenger to 

retrieve an underseat life vest and the ease of retrieval. This work may lead 

to additonal guidance on the location of personal flotation devices. 

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FAA’s research may also indicate a need for additional guidance on the use 

of personal flotation devices. In a 1998 report on ditching aircraft and water 

survival, FAA found that airlines differed in their instructions to passengers 

on how to use personal flotation devices.7

 For example, some airlines 

advise that passengers hold the cushions in front of their bodies, rest their 

chins on the cushions, wrap their arms around the cushions with their 

hands grasping the outside loops, and float vertically in the water. Other 

airlines suggest that passengers lie forward on the cushions, grasp and hold 

the loops beneath them, and float horizontally. FAA also reported that 

airlines’ flight attendant training programs differed in their instructions on 

how to don life vests and when to inflate them. 

7

LB & M Associates, Inc., and Garnet A. McLean, Analysis of Ditching and Water Survival 

Training Programs of Major Airframe Manufacturers and Airlines, CAMI [DOT/FAA/AM98/19], (Washington, D.C.). 

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Summaries of General Cabin Occupant Safety 

and Health Advancements 

This appendix presents information on the background and status of 

potential advancements in general cabin occupant safety and health that 

we identified, including the following: 

• advanced warnings of turbulence; 

• preparations for in-flight medical emergencies; 

•	 reductions in health risks to passengers with certain medical conditions, 

including deep vein thrombosis; and 

• improved awareness of radiation exposure. 

This appendix also discusses occupational safety and health standards for 

the flight attendant workforce. 

Advanced Warnings of 

Turbulence 

Background 	 According to FAA, the leading cause of in-flight injuries for cabin 

occupants is turbulence. In June 1995, following two serious events 

involving turbulence, FAA issued a public advisory to airlines urging the 

use of seat belts at all times when passengers are seated, but concluded 

that the existing rules did not require strengthening. In May 2000, FAA 

instituted a public awareness campaign, called Turbulence Happens, to 

stress the importance of wearing safety belts to the flying public. 

Because of the potential for injury from unexpected turbulence, ongoing 

research is attempting to find ways to better identify areas of turbulence so 

that pilots can take corrective action to avoid it. In addition, FAA’s July 2003 

draft strategic plan targets a 33 percent reduction in the number of 

turbulence injuries to cabin occupants by 2008—from an annual average of 

15 injuries per year for fiscal years 2000 through 2002 to no more than 10 

injuries per year. 

Status	 FAA is currently evaluating new airborne weather radar and other 

technologies to improve the timeliness of warnings to passengers and flight 

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attendants about impending turbulence. For example, the Turbulence 

Product Development Team, within FAA’s Aviation Weather Research 

Program, has developed a system to measure turbulence and downlink the 

information in real time from commercial air carriers. The International 

Civil Aviation Organization has approved this system as an international 

standard. Ongoing research includes (1) detecting turbulence in flight and 

reporting its intensity to augment pilots’ reports, (2) detecting turbulence 

remotely from the ground or in the air using radar, (3) detecting turbulence 

remotely using LIDAR1

 or the Global Positioning System’s constellation of 

satellites, and (4) forecasting the likelihood of turbulence over the 

continental United States during the next 12 hours. Prototypes of the inflight detection system have been installed on 100 737-300s operated by 

United Airlines, and two other domestic air carriers have expressed an 

interest in using the prototype. FAA also plans to improve (1) training on 

standard operating procedures to reduce injuries from turbulence, (2) the 

dissemination of pilots’ reports of turbulence, and (3) the timeliness of 

weather forecasts to identify turbulent areas. Furthermore, FAA 

encourages and some airlines require passengers to keep their seatbelts 

fastened when seated to help avoid injuries from unexpected turbulence. 

Currently, pilots rely primarily on other pilots to report when and where 

(e.g., specific altitudes and routes) they have encountered turbulent 

conditions en route to their destinations; however, these reports do not 

accurately identify the location, time, and intensity of the turbulence. 

Further research and testing will be required to develop technology to 

accurately identify turbulence and to make the technology affordable to the 

airlines, which would ultimately bear the cost of upgrading their aircraft 

fleets. 

Preparations for Inflight Medical 

Emergencies 

1

LIDAR (LIght Detection And Ranging) is a technology that can measure the distance, speed, 

rotation, and chemical composition and concentration of a remote target, such as 

turbulence. 

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Background	 The Aviation Medical Assistance Act of 1998 directed FAA to determine 

whether the current minimum requirements for air carriers’ emergency 

medical equipment and crewmember emergency medical training should 

be modified. In accordance with the act, FAA collected data for a year on 

in-flight deaths and near deaths and concluded that enhancements to 

medical kits and a requirement for airlines to carry automatic external 

defibrillators were warranted. Specifically, the agency found that these 

improvements would allow cabin crewmembers to deal with a broader 

range of in-flight emergencies. 

Status	 On April 12, 2001, FAA issued a final rule requiring air carriers to equip 

their aircraft with enhanced emergency medical kits and automatic 

external defibrillators by May 12, 2004. Most U.S. airlines have installed this 

equipment in advance of the deadline. 

In the future, new larger aircraft may require additional improvements to 

meet passengers’ medical needs. For example, new large transport aircraft, 

such as the Airbus A-380, will have the capacity to carry about 555 people 

on long-distance flights. Some aviation safety experts are concerned that 

with the large number of passengers on these aircraft, the number of inflight medical emergencies will increase and additional precautions for inflight medical emergencies (e.g., dedicating an area for passengers who 

experience medical emergencies in flight) should be considered. Airbus 

has proposed a medical room in the cabin of its A-380 as an option for its 

customers. 

Reducing Health Risks 

to Passengers with 

Certain Medical 

Conditions 

Background	 Passengers with certain medical conditions (e.g., heart and lung diseases) 

can be at higher risk of health-related complications from air travel than 

the general population. For example, passengers who have limited heart or 

lung function or have recently had surgery or a leg injury can be at greater 

risk of developing a condition known as deep vein thrombosis (DVT) or 

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travelers’ thrombosis, in which blood clots can develop in the deep veins of 

the legs from extended periods of inactivity. Air travel has not been linked 

definitively to the development of DVT, but remaining seated for extended 

periods of time, whether in one’s home or on a long-distance flight, can 

cause blood to pool in the legs and increase the chances of developing DVT. 

In a small percentage of cases, the clots can break free and travel to the 

lungs, with fatal results. 

In addition, the reduced levels of oxygen available to passengers in-flight 

can have detrimental health effects on passengers with heart, circulatory, 

and respiratory disorders because lower levels of oxygen in the air produce 

lower levels of oxygen in the body—a condition known as hypoxia. 

Furthermore, changes in cabin pressure (primarily when the aircraft 

ascends and descends) can negatively affect ear, nose, and throat 

conditions and pose problems for those flying after certain types of surgery 

(e.g., abdominal, cardiac, and eye surgery). 

Status 	 Information on the potential effects of air travel on passengers with certain 

medical conditions is available; however, additional research, such as on 

the potential relationship between DVT and air travel, is ongoing. The 

National Research Council, in a 2001 report on airliner cabin air quality, 

recommended, among other things, that FAA increase efforts to provide 

information on health issues related to air travel to crewmembers, 

passengers, and health professionals. According to FAA’s Federal Air 

Surgeon, since this recommendation was received, the agency has 

redoubled its efforts to make information and recommendations on air 

travel and medical issues available through its Web site 

www.cami.jccbi.gov/aam-400/PassengerHandS.htm. This site also includes 

links to the Web sites of other organizations with safety and health 

information for air travelers, such as the Aerospace Medical Association, 

the American Family Physician (Medical Advice for Commercial Air 

Travelers), and the Sinus Care Center (Ears, Altitude, and Airplane Travel), 

and videos on safety and health issues for pilots and air travelers. The 

Aerospace Medical Association’s Web site, 

http://www.asma.org/publication.html, includes guidance for physicians to 

use in advising passengers about the potential risks of flying based on their 

medical conditions, as well as information for passengers to use in 

determining whether air travel is advisable given their medical conditions. 

Furthermore, some airlines currently encourage passengers to do exercises 

while seated, to get up and walk around during long flights, or to do both to 

improve blood circulation; however, walking around the airplane can also 

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put passengers at risk of injuries from unexpected turbulence. In addition, 

a prototype of a seat has been designed with imbedded sensors, which 

record the movement of a passenger and send this information to the cabin 

crew for monitoring. The crew would then be able to track passengers 

seated for a long time and could suggest that these passengers exercise in 

their seats or walk in the cabin aisles to enhance circulation. 

While FAA’s Web site on passenger and pilot safety and health provides 

links to related Web sites and videos (e.g., cabin occupant safety and health 

issues), historically, the agency has not tracked who uses its Web site or 

how frequently it is used to monitor the traveling public’s awareness and 

use of this site. Agency officials told us that they plan to install a counter 

capability on its Civil Aerospace Medical Institute Web site by the end of 

August 2003 to track the number of visits to its aircrew and passenger 

health and safety Web site. The World Health Organization has initiated a 

study to help determine if a linkage exists between DVT and air travel. 

Further, FAA developed a brochure on DVT that has been distributed to 

aviation medical examiners and cited in the Federal Air Surgeon’s Bulletin. 

The brochure is aimed at passengers rather than airlines and suggests 

exercises that can be done to promote circulation. 

Improved Awareness 

of Radiation Exposure 

Background	 Pilots, flight attendants, and passengers who fly frequently are exposed to 

cosmic radiation at higher levels (on a cumulative basis) than the average 

airline passenger and the general public living at or near sea level. This is 

because they routinely fly at high altitudes, which places them closer to 

outer space, which is the primary source of this radiation. High levels of 

radiation have been linked to an increased risk of cancer and potential 

harm to fetuses. The amount of radiation that flight attendants and frequent 

fliers are exposed to—referred to as the dose—depends on four primary 

factors: (1) the amount of time spent in flight; (2) the latitude of the flight— 

exposure increases at higher latitudes; for example, at the same altitude, 

radiation levels at the poles are about twice those at the equator; (3) the 

altitude of the flight—exposure is greater at high altitudes because the 

layer of protective atmosphere becomes thinner; and (4) solar activity— 

exposure is higher when solar activity increases, as it does every 11 years 

or so. Peak periods of solar activity, which can increase exposure to 

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radiation by 10 to 20 times, are sometimes called solar storms or solar 

flares. 

Status	 FAA’s Web site currently makes available guidance on radiation exposure 

levels and risks for flight and cabin crewmembers, as well as a system for 

calculating radiation doses from flying specific routes and specific 

altitudes. To increase crewmembers’ awareness of in-flight radiation 

exposure, FAA issued two Advisory Circulars for crewmembers. The first 

Advisory Circular, issued in 1990, provided information on (1) cosmic 

radiation and air shipments of radioactive material as sources of radiation 

exposure during air travel; (2) guidelines for exposure to radiation; (3) 

estimates of the amounts of radiation received on air carriers’ flights on 

various routes to and from, or within, the contiguous United States; and (4) 

examples of calculations for estimating health risks from exposure to 

radiation. The second Advisory Circular, issued in 1994, recommended 

training for crewmembers to inform them about in-flight radiation 

exposure and known associated health risks and to assist them in making 

informed decisions about their work on commercial air carriers. The 

circular provided a possible outline of courses, but left it to air carriers to 

gather the subject matter materials. To facilitate the monitoring of radiation 

exposure levels by airliner crewmembers and the public (e.g., frequent 

fliers), FAA has developed a computer model, which is publicly available 

via the agency’s Web site. This Web site also provides guidance and 

recommendations on limiting radiation exposure. However, it is unclear to 

what extent flight attendants, flight crews, and frequent fliers are aware of 

and use FAA’s Web site to track the radiation exposure levels they accrue 

from flying. Agency officials told us that they plan to install a counter 

capability its Civil Aerospace Medical Institute Web site by the end of 

August 2003, to track the number of visits to its aircrew and passenger 

health and safety Web site. FAA also plans to issue an Advisory Circular by 

early next year, which incorporates the findings of a just completed FAA 

report, “What Aircrews Should Know About Their Occupational Exposure 

to Ionizing Radiation.” This Advisory Circular will include recommended 

actions for aircrew and information on solar flare event notification of 

aircrew. While FAA provides guidance and recommendations on limiting 

the levels of cosmic radiation that flight attendants and pilots are exposed 

to, it has not developed any regulations. 

In contrast, the European Union issued a directive for workers in May 1996, 

including air carrier crewmembers (cabin and flight crews) and the general 

public, on basic safety and health protections against dangers arising from 

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ionizing radiation. This directive set dose limits and required air carriers to 

(1) assess and monitor the exposure of all crewmembers to avoid 

exceeding exposure limits, (2) work with those individuals at risk of high 

exposure levels to adjust their work or flight schedules to reduce those 

levels, and (3) inform crewmembers of the health risks that their work 

involves from exposure to radiation. It also required airlines to work with 

female crewmembers, when they announce a pregnancy, to avoid exposing 

the fetus to harmful levels of radiation. This directive was binding for all 

European Union member states and became effective in May 2000. 

According to European safety officials, pregnant crewmembers are often 

given the option of an alternative job with the airline on the ground to avoid 

radiation exposure to their fetuses. Furthermore, when flight attendants 

and pilots reach recommended exposure limits, European air carriers work 

with crewmembers to limits or change their subsequent flights and 

destinations to minimize exposure levels for the balance of the year. Some 

air carriers ground crewmembers when they reach annual exposure limits 

or change their subsequent flights and destinations to minimize exposure 

levels for the balance of the year. 

Occupational Safety 

and Health Standards 

for Flight Attendants 

Background	 In 1975, FAA assumed responsibility from the Occupational Health and 

Safety Administration (OSHA) for establishing safety and health standards 

for flight attendants. However, FAA has only recently begun to take action 

to provide this workforce with OSHA-like protections. For example, in 

August 2000, FAA and OSHA entered into a memorandum of understanding 

and issued a joint report in December 2000, which identified safety and 

health concerns for the flight attendant workforce and the extent to which 

OSHA-type standards could be used without compromising aviation safety. 

On September 29, 2001, the DOT Office of the Inspector General (DOT IG) 

reported that FAA had made little progress toward providing flight 

attendants with workplace protections and urged FAA to address the 

recommendations in the December 2000 report and move forward with 

setting safety and health standards for the flight attendant workforce. In 

April 2002, the DOT IG reported that FAA and OSHA had made no progress 

since it issued its report in September 2001. According to FAA officials, the 

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joint FAA and OSHA effort was put on hold because of other priorities that 

arose in response to the events of September 11, 2001. 

Status	 FAA has not yet established occupational safety and health standards to 

protect the flight attendant workforce. FAA is conducting research and 

collecting data on flight attendants’ injuries and illnesses. 

On March 4, 2003, FAA announced the creation of a voluntary program for 

air carriers, called the Aviation Safety and Health Partnership Program. 

Through this program, the agency intends to enter into partnership 

agreements with participating air carriers, which will, at a minimum, make 

data on their employees’ injuries and illnesses available to FAA for 

collection and analysis. FAA will then establish an Aviation Safety and 

Health Program Aviation Rule-Making Committee to provide advice and 

recommendations to 

•	 develop the scope and core elements of the partnership program 

agreement; 

• review and analyze the data on employees’ injuries and illnesses; 

•	 identify the scope and extent of systematic trends in employees’ injuries 

and illnesses; 

•	 recommend remedies to FAA that use all current FAA protocols, 

including rule-making activities if warranted, to abate hazards to 

employees; and 

•	 create any other advisory and oversight functions that FAA deems 

necessary. 

FAA plans to select members to provide a balance of viewpoints, interests, 

and expertise. The program preserves FAA’s complete and exclusive 

responsibility for determining whether proposed abatements of safety and 

health hazards would compromise or negatively affect aviation safety. 

FAA is also funding research through the National Institute for 

Occupational Safety and Health (NIOSH) to, among other things, determine 

the effects of flying on the reproductive health of flight attendants, much of 

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which has been completed.2 FAA plans to monitor cabin air quality on a 

selected number of flights, which will help it set standards for the flight 

attendant workforce. 

The Association of Flight Attendants has collected a large body of data on 

flight attendants’ injuries and illnesses, which it considers sufficient for use 

in establishing safety and health standards for its workforce. Officials from 

the association do not believe that FAA needs to collect additional data 

before starting the standard-setting process. 

The European Union has occupational safety and health standards in place 

to protect flight attendants, including standards for monitoring their levels 

of radiation exposure. An official from an international association of flight 

attendants told us that while flight attendants in Europe have concerns 

similar to those of flight attendants in the United States (e.g., concerns 

about air quality in airliner cabins), the European Union places a heavier 

emphasis on worker safety and health, including safety and health 

protections for flight attendants. 

2

NIOSH is also conducting research on airliner cabin environmental quality, respiratory 

symptoms of flight attendants, and disease transmission. 

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Appendix VIII 

Application of a Cost Analysis Methodology to 

Inflatable Lap Belts 

The following illustrates how a cost analysis might be conducted on each of 

the potential advancements discussed in this report. Costs estimated 

through this analysis could then be weighed against the potential lives 

saved and injuries avoided from implementing the advancements. This 

methodology would allow advancements to be compared using comparable 

cost data that when combined with similar analyses of effectiveness to help 

decisionmakers determine which advancements would be most effective in 

saving lives and avoiding injuries, taking into account their costs. The 

methodology provides for developing a cost estimate despite significant 

uncertainties by making use of historical data (e.g, historical variations in 

fuel prices) and best engineering judgments (e.g., how much weight an 

advancement will add and how much it will cost to install, operate, and 

maintain). The methodology formally takes into account the major sources 

of uncertainty and from that information develops a range of cost 

estimates, including a most likely cost estimate. Through a common 

approach for analyzing costs, the methodology facilitates the development 

of comparable estimates. This methodology can be applied to 

advancements in various stages of development. 

Inflatable Lap Belts	 Inflatable lap belts are designed to protect passengers from a fatal impact 

with the interior of the airplane, the most common cause of death in 

survivable accidents. Inflatable seat belts adapt advanced automobile 

technology to airplane seats in the form of seat belts with air bags 

embedded in them. Several hundred of these seatbelt airbags have been 

installed in commercial airliners in bulkhead rows. 

Summary of Results	 We calculated that requiring these belts on an average-sized airplane in the 

U.S. passenger fleet would be likely to cost from $98,000 to $198,000 and to 

average about $140,000 over the life of the airplane. On an annual basis, the 

cost would be likely to range from $8,000 to $17,000 and to average $12,000. 

We considered several factors to explain this range of possible costs. The 

installation price of these belts is subject to uncertainty because of their 

limited production to date. In addition, these belts add weight to an 

aircraft, resulting in additional fuel costs. Fuel costs depend on the price of 

jet fuel and on how many hours the average airplane operates, both subject 

to uncertainty. Table 5 lists the results of our cost analysis for an averagesized airplane in the U.S. fleet. 

Page 115 GAO-04-33 Airliner Cabin Occupant Safety and Health 
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Application of a Cost Analysis Methodology 


to Inflatable Lap Belts


Table 4: Costs to Equip an Average-sized Airplane in the U.S. Fleet with Inflatable 

Lap Seat Belts, Estimated under Alternative Scenarios (In 2002 discounted dollars) 

Cost scenario 

Cost Low Average High 95 percentilea 

Life-cycle $98,000 $140,000 $198,000 $186,000 

Annualized $8,000 $12,000 $17,000 $16,000 

Per ticket

b $0.08 $0.13 $0.19 $0.18 

Source: GAO analysis. 

a

For example, a 95 percentile estimate means that there is a 95 percent probability that the total lifecycle costs per airplane will be $186,000 or less. 

b

Cost rounded to the nearest cent. 

According to our analysis, the life-cycle and annualized cost estimates in 

table 5 are influenced most by variations in jet fuel prices, followed by the 

average number of hours flown per year and the installation price of the 

belts. The cost per ticket is influenced most by variations in jet fuel prices, 

followed by the average number of hours flown per year, the number of 

aircraft in the U.S. fleet, and the number of passenger tickets issued. 

Methodology	 To analyze the cost of inflatable lap belts, we collected data on key cost 

variables from a variety of sources. Information on the belts’ installation 

price, annual maintenance and refurbishment costs, and added weight was 

obtained from belt manufacturers. Historical information on jet fuel prices, 

extra gallons of jet fuel consumed by a heavier airplane, average hours 

flown per year, average number of seats per airplane, number of airplanes 

in the U.S. fleet, and number of passenger tickets issued per year was 

obtained from FAA and DOT’s Office of Aviation Statistics. 

To account for variation in the values of these cost variables, we performed 

a Monte Carlo simulation.

1

 In this simulation, values were randomly drawn 

10,000 times from probability distributions characterizing possible values 

1

“Monte Carlo simulation is a widely used computational method for generating probability 

distributions of variables that depend on other variables or parameters represented as 

probability distributions. Monte Carlo methods are to be contrasted with the deterministic 

methods used to generate specific single number or point estimates.” Susan Poulter, “Monte 

Carlo Simulation in Environmental Risk Assessment - Science, Policy And Legal Issues,” 9 

Risk: Health, Safety & Environment 7 [Winter 1998]. 

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Application of a Cost Analysis Methodology 


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for the number of seat belts per airplane, seat belt installation price, jet fuel 

price, number of passenger tickets, number of airplanes, and hours flown.2 

This simulation resulted in forecasts of the life-cycle cost per airplane, the 

annualized cost per airplane, and the cost per ticket. 

Major assumptions in the cost analysis are described by probability 

distributions selected for these cost variables. For jet fuel prices, average 

number of hours flown per year, and average number of seats per airplane, 

historical data were matched against possible probability distributions.3 

Mathematical tests were performed to find the best fit between each 

probability distribution and the data set’s distribution. For the installation 

price, number of passenger tickets, and number of airplanes, less 

information was available.4 For these variables, we selected probability 

distributions that are widely used by researchers. Table 6 lists the type of 

probability distribution and the relevant parameters of each distribution for 

the cost variables. 

Table 5: Key Assumptions 

Type of Mean or Standard 

Cost variable distribution average deviation Minimum Maximum Likeliest Mode Scale 

Fuel price lognormal $0.93 $0.33 

Seats lognormal 161 8 

Installation price triangular $300 $600 $450 

Hours extreme value 2,353 2,643 539 

Airplanes normal 4,438 399 

Tickets normal 419 35 

Source: GAO analysis. 

2

A probability distribution is a set of all possible events and their associated probabilities. 

Probability refers to the likelihood of an event. 

3

Historical data from 1975 through 2001 were available for the number of seats per plane, 

and from 1977 through 2002 for jet fuel prices. Aircraft utilization data for 2001 were 

available for annual hours per aircraft. 

4

Historical data from 1995 through 2001 were available for the number of planes and tickets. 

Page 117 GAO-04-33 Airliner Cabin Occupant Safety and Health 
Appendix IX 

GAO Contacts and Staff Acknowledgments


GAO Contacts	 Gerald L. Dillingham (202) 512-2834 

Glen Trochelman (202) 512-2834 

Beverly Norwood (202) 512-2834 

Staff 	 In addition to those named above, Chuck Bausell, Helen Chung, Elizabeth 

Eisenstadt, David Ehrlich, Bert Japikse, Sarah Lynch, Sara Ann Acknowledgments Moessbauer, and Anthony Patterson made key contributions to this report. 

(540017) Page 118 GAO-04-33 Airliner Cabin Occupant Safety and Health 
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